543 lines
21 KiB
Python
543 lines
21 KiB
Python
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# searchAgents.py
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# ---------------
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# Licensing Information: You are free to use or extend these projects for
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# educational purposes provided that (1) you do not distribute or publish
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# solutions, (2) you retain this notice, and (3) you provide clear
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# attribution to UC Berkeley, including a link to http://ai.berkeley.edu.
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#
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# Attribution Information: The Pacman AI projects were developed at UC Berkeley.
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# The core projects and autograders were primarily created by John DeNero
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# (denero@cs.berkeley.edu) and Dan Klein (klein@cs.berkeley.edu).
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# Student side autograding was added by Brad Miller, Nick Hay, and
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# Pieter Abbeel (pabbeel@cs.berkeley.edu).
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"""
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This file contains all of the agents that can be selected to control Pacman. To
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select an agent, use the '-p' option when running pacman.py. Arguments can be
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passed to your agent using '-a'. For example, to load a SearchAgent that uses
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depth first search (dfs), run the following command:
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> python pacman.py -p SearchAgent -a fn=depthFirstSearch
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Commands to invoke other search strategies can be found in the project
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description.
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Please only change the parts of the file you are asked to. Look for the lines
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that say
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"*** YOUR CODE HERE ***"
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The parts you fill in start about 3/4 of the way down. Follow the project
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description for details.
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Good luck and happy searching!
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"""
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from game import Directions
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from game import Agent
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from game import Actions
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import util
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import time
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import search
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class GoWestAgent(Agent):
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"An agent that goes West until it can't."
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def getAction(self, state):
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"The agent receives a GameState (defined in pacman.py)."
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if Directions.WEST in state.getLegalPacmanActions():
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return Directions.WEST
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else:
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return Directions.STOP
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#######################################################
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# This portion is written for you, but will only work #
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# after you fill in parts of search.py #
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#######################################################
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class SearchAgent(Agent):
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"""
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This very general search agent finds a path using a supplied search
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algorithm for a supplied search problem, then returns actions to follow that
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path.
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As a default, this agent runs DFS on a PositionSearchProblem to find
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location (1,1)
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Options for fn include:
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depthFirstSearch or dfs
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breadthFirstSearch or bfs
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Note: You should NOT change any code in SearchAgent
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"""
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def __init__(self, fn='depthFirstSearch', prob='PositionSearchProblem', heuristic='nullHeuristic'):
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# Warning: some advanced Python magic is employed below to find the right functions and problems
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# Get the search function from the name and heuristic
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if fn not in dir(search):
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raise AttributeError, fn + ' is not a search function in search.py.'
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func = getattr(search, fn)
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if 'heuristic' not in func.func_code.co_varnames:
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print('[SearchAgent] using function ' + fn)
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self.searchFunction = func
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else:
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if heuristic in globals().keys():
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heur = globals()[heuristic]
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elif heuristic in dir(search):
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heur = getattr(search, heuristic)
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else:
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raise AttributeError, heuristic + ' is not a function in searchAgents.py or search.py.'
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print('[SearchAgent] using function %s and heuristic %s' % (fn, heuristic))
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# Note: this bit of Python trickery combines the search algorithm and the heuristic
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self.searchFunction = lambda x: func(x, heuristic=heur)
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# Get the search problem type from the name
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if prob not in globals().keys() or not prob.endswith('Problem'):
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raise AttributeError, prob + ' is not a search problem type in SearchAgents.py.'
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self.searchType = globals()[prob]
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print('[SearchAgent] using problem type ' + prob)
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def registerInitialState(self, state):
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"""
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This is the first time that the agent sees the layout of the game
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board. Here, we choose a path to the goal. In this phase, the agent
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should compute the path to the goal and store it in a local variable.
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All of the work is done in this method!
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state: a GameState object (pacman.py)
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"""
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if self.searchFunction == None: raise Exception, "No search function provided for SearchAgent"
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starttime = time.time()
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problem = self.searchType(state) # Makes a new search problem
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self.actions = self.searchFunction(problem) # Find a path
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totalCost = problem.getCostOfActions(self.actions)
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print('Path found with total cost of %d in %.1f seconds' % (totalCost, time.time() - starttime))
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if '_expanded' in dir(problem): print('Search nodes expanded: %d' % problem._expanded)
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def getAction(self, state):
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"""
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Returns the next action in the path chosen earlier (in
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registerInitialState). Return Directions.STOP if there is no further
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action to take.
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state: a GameState object (pacman.py)
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"""
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if 'actionIndex' not in dir(self): self.actionIndex = 0
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i = self.actionIndex
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self.actionIndex += 1
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if i < len(self.actions):
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return self.actions[i]
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else:
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return Directions.STOP
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class PositionSearchProblem(search.SearchProblem):
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"""
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A search problem defines the state space, start state, goal test, successor
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function and cost function. This search problem can be used to find paths
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to a particular point on the pacman board.
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The state space consists of (x,y) positions in a pacman game.
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Note: this search problem is fully specified; you should NOT change it.
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"""
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def __init__(self, gameState, costFn = lambda x: 1, goal=(1,1), start=None, warn=True, visualize=True):
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"""
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Stores the start and goal.
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gameState: A GameState object (pacman.py)
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costFn: A function from a search state (tuple) to a non-negative number
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goal: A position in the gameState
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"""
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self.walls = gameState.getWalls()
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self.startState = gameState.getPacmanPosition()
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if start != None: self.startState = start
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self.goal = goal
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self.costFn = costFn
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self.visualize = visualize
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if warn and (gameState.getNumFood() != 1 or not gameState.hasFood(*goal)):
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print 'Warning: this does not look like a regular search maze'
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# For display purposes
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self._visited, self._visitedlist, self._expanded = {}, [], 0 # DO NOT CHANGE
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def getStartState(self):
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return self.startState
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def isGoalState(self, state):
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isGoal = state == self.goal
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# For display purposes only
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if isGoal and self.visualize:
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self._visitedlist.append(state)
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import __main__
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if '_display' in dir(__main__):
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if 'drawExpandedCells' in dir(__main__._display): #@UndefinedVariable
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__main__._display.drawExpandedCells(self._visitedlist) #@UndefinedVariable
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return isGoal
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def getSuccessors(self, state):
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"""
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Returns successor states, the actions they require, and a cost of 1.
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As noted in search.py:
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For a given state, this should return a list of triples,
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(successor, action, stepCost), where 'successor' is a
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successor to the current state, 'action' is the action
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required to get there, and 'stepCost' is the incremental
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cost of expanding to that successor
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"""
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successors = []
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for action in [Directions.NORTH, Directions.SOUTH, Directions.EAST, Directions.WEST]:
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x,y = state
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dx, dy = Actions.directionToVector(action)
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nextx, nexty = int(x + dx), int(y + dy)
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if not self.walls[nextx][nexty]:
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nextState = (nextx, nexty)
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cost = self.costFn(nextState)
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successors.append( ( nextState, action, cost) )
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# Bookkeeping for display purposes
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self._expanded += 1 # DO NOT CHANGE
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if state not in self._visited:
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self._visited[state] = True
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self._visitedlist.append(state)
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return successors
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def getCostOfActions(self, actions):
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"""
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Returns the cost of a particular sequence of actions. If those actions
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include an illegal move, return 999999.
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"""
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if actions == None: return 999999
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x,y= self.getStartState()
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cost = 0
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for action in actions:
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# Check figure out the next state and see whether its' legal
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dx, dy = Actions.directionToVector(action)
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x, y = int(x + dx), int(y + dy)
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if self.walls[x][y]: return 999999
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cost += self.costFn((x,y))
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return cost
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class StayEastSearchAgent(SearchAgent):
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"""
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An agent for position search with a cost function that penalizes being in
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positions on the West side of the board.
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The cost function for stepping into a position (x,y) is 1/2^x.
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"""
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def __init__(self):
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self.searchFunction = search.uniformCostSearch
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costFn = lambda pos: .5 ** pos[0]
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self.searchType = lambda state: PositionSearchProblem(state, costFn, (1, 1), None, False)
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class StayWestSearchAgent(SearchAgent):
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"""
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An agent for position search with a cost function that penalizes being in
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positions on the East side of the board.
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The cost function for stepping into a position (x,y) is 2^x.
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"""
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def __init__(self):
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self.searchFunction = search.uniformCostSearch
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costFn = lambda pos: 2 ** pos[0]
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self.searchType = lambda state: PositionSearchProblem(state, costFn)
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def manhattanHeuristic(position, problem, info={}):
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"The Manhattan distance heuristic for a PositionSearchProblem"
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xy1 = position
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xy2 = problem.goal
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return abs(xy1[0] - xy2[0]) + abs(xy1[1] - xy2[1])
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def euclideanHeuristic(position, problem, info={}):
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"The Euclidean distance heuristic for a PositionSearchProblem"
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xy1 = position
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xy2 = problem.goal
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return ( (xy1[0] - xy2[0]) ** 2 + (xy1[1] - xy2[1]) ** 2 ) ** 0.5
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#####################################################
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# This portion is incomplete. Time to write code! #
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#####################################################
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class CornersProblem(search.SearchProblem):
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"""
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This search problem finds paths through all four corners of a layout.
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You must select a suitable state space and successor function
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"""
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def __init__(self, startingGameState):
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"""
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Stores the walls, pacman's starting position and corners.
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"""
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self.walls = startingGameState.getWalls()
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self.startingPosition = startingGameState.getPacmanPosition()
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top, right = self.walls.height-2, self.walls.width-2
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self.corners = ((1,1), (1,top), (right, 1), (right, top))
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for corner in self.corners:
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if not startingGameState.hasFood(*corner):
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print 'Warning: no food in corner ' + str(corner)
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self._expanded = 0 # DO NOT CHANGE; Number of search nodes expanded
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# Please add any code here which you would like to use
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# in initializing the problem
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"*** YOUR CODE HERE ***"
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def getStartState(self):
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"""
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Returns the start state (in your state space, not the full Pacman state
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space)
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"""
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"*** YOUR CODE HERE ***"
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util.raiseNotDefined()
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def isGoalState(self, state):
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"""
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Returns whether this search state is a goal state of the problem.
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"""
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"*** YOUR CODE HERE ***"
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util.raiseNotDefined()
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def getSuccessors(self, state):
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"""
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Returns successor states, the actions they require, and a cost of 1.
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As noted in search.py:
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For a given state, this should return a list of triples, (successor,
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action, stepCost), where 'successor' is a successor to the current
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state, 'action' is the action required to get there, and 'stepCost'
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is the incremental cost of expanding to that successor
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"""
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successors = []
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for action in [Directions.NORTH, Directions.SOUTH, Directions.EAST, Directions.WEST]:
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# Add a successor state to the successor list if the action is legal
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# Here's a code snippet for figuring out whether a new position hits a wall:
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# x,y = currentPosition
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# dx, dy = Actions.directionToVector(action)
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# nextx, nexty = int(x + dx), int(y + dy)
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# hitsWall = self.walls[nextx][nexty]
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"*** YOUR CODE HERE ***"
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self._expanded += 1 # DO NOT CHANGE
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return successors
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def getCostOfActions(self, actions):
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"""
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Returns the cost of a particular sequence of actions. If those actions
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include an illegal move, return 999999. This is implemented for you.
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"""
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if actions == None: return 999999
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x,y= self.startingPosition
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for action in actions:
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dx, dy = Actions.directionToVector(action)
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x, y = int(x + dx), int(y + dy)
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if self.walls[x][y]: return 999999
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return len(actions)
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def cornersHeuristic(state, problem):
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"""
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A heuristic for the CornersProblem that you defined.
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state: The current search state
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(a data structure you chose in your search problem)
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problem: The CornersProblem instance for this layout.
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This function should always return a number that is a lower bound on the
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shortest path from the state to a goal of the problem; i.e. it should be
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admissible (as well as consistent).
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"""
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corners = problem.corners # These are the corner coordinates
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walls = problem.walls # These are the walls of the maze, as a Grid (game.py)
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"*** YOUR CODE HERE ***"
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return 0 # Default to trivial solution
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class AStarCornersAgent(SearchAgent):
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"A SearchAgent for FoodSearchProblem using A* and your foodHeuristic"
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def __init__(self):
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self.searchFunction = lambda prob: search.aStarSearch(prob, cornersHeuristic)
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self.searchType = CornersProblem
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class FoodSearchProblem:
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"""
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A search problem associated with finding the a path that collects all of the
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food (dots) in a Pacman game.
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A search state in this problem is a tuple ( pacmanPosition, foodGrid ) where
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pacmanPosition: a tuple (x,y) of integers specifying Pacman's position
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foodGrid: a Grid (see game.py) of either True or False, specifying remaining food
|
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"""
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def __init__(self, startingGameState):
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self.start = (startingGameState.getPacmanPosition(), startingGameState.getFood())
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self.walls = startingGameState.getWalls()
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self.startingGameState = startingGameState
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self._expanded = 0 # DO NOT CHANGE
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self.heuristicInfo = {} # A dictionary for the heuristic to store information
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def getStartState(self):
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return self.start
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def isGoalState(self, state):
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return state[1].count() == 0
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def getSuccessors(self, state):
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"Returns successor states, the actions they require, and a cost of 1."
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successors = []
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self._expanded += 1 # DO NOT CHANGE
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for direction in [Directions.NORTH, Directions.SOUTH, Directions.EAST, Directions.WEST]:
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x,y = state[0]
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dx, dy = Actions.directionToVector(direction)
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nextx, nexty = int(x + dx), int(y + dy)
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if not self.walls[nextx][nexty]:
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nextFood = state[1].copy()
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nextFood[nextx][nexty] = False
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successors.append( ( ((nextx, nexty), nextFood), direction, 1) )
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return successors
|
||
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|
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def getCostOfActions(self, actions):
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"""Returns the cost of a particular sequence of actions. If those actions
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include an illegal move, return 999999"""
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x,y= self.getStartState()[0]
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cost = 0
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for action in actions:
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# figure out the next state and see whether it's legal
|
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dx, dy = Actions.directionToVector(action)
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x, y = int(x + dx), int(y + dy)
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if self.walls[x][y]:
|
||
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return 999999
|
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cost += 1
|
||
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return cost
|
||
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|
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|
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class AStarFoodSearchAgent(SearchAgent):
|
||
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"A SearchAgent for FoodSearchProblem using A* and your foodHeuristic"
|
||
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def __init__(self):
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||
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self.searchFunction = lambda prob: search.aStarSearch(prob, foodHeuristic)
|
||
|
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self.searchType = FoodSearchProblem
|
||
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|
||
|
|
def foodHeuristic(state, problem):
|
||
|
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"""
|
||
|
|
Your heuristic for the FoodSearchProblem goes here.
|
||
|
|
|
||
|
|
This heuristic must be consistent to ensure correctness. First, try to come
|
||
|
|
up with an admissible heuristic; almost all admissible heuristics will be
|
||
|
|
consistent as well.
|
||
|
|
|
||
|
|
If using A* ever finds a solution that is worse uniform cost search finds,
|
||
|
|
your heuristic is *not* consistent, and probably not admissible! On the
|
||
|
|
other hand, inadmissible or inconsistent heuristics may find optimal
|
||
|
|
solutions, so be careful.
|
||
|
|
|
||
|
|
The state is a tuple ( pacmanPosition, foodGrid ) where foodGrid is a Grid
|
||
|
|
(see game.py) of either True or False. You can call foodGrid.asList() to get
|
||
|
|
a list of food coordinates instead.
|
||
|
|
|
||
|
|
If you want access to info like walls, capsules, etc., you can query the
|
||
|
|
problem. For example, problem.walls gives you a Grid of where the walls
|
||
|
|
are.
|
||
|
|
|
||
|
|
If you want to *store* information to be reused in other calls to the
|
||
|
|
heuristic, there is a dictionary called problem.heuristicInfo that you can
|
||
|
|
use. For example, if you only want to count the walls once and store that
|
||
|
|
value, try: problem.heuristicInfo['wallCount'] = problem.walls.count()
|
||
|
|
Subsequent calls to this heuristic can access
|
||
|
|
problem.heuristicInfo['wallCount']
|
||
|
|
"""
|
||
|
|
position, foodGrid = state
|
||
|
|
"*** YOUR CODE HERE ***"
|
||
|
|
return 0
|
||
|
|
|
||
|
|
class ClosestDotSearchAgent(SearchAgent):
|
||
|
|
"Search for all food using a sequence of searches"
|
||
|
|
def registerInitialState(self, state):
|
||
|
|
self.actions = []
|
||
|
|
currentState = state
|
||
|
|
while(currentState.getFood().count() > 0):
|
||
|
|
nextPathSegment = self.findPathToClosestDot(currentState) # The missing piece
|
||
|
|
self.actions += nextPathSegment
|
||
|
|
for action in nextPathSegment:
|
||
|
|
legal = currentState.getLegalActions()
|
||
|
|
if action not in legal:
|
||
|
|
t = (str(action), str(currentState))
|
||
|
|
raise Exception, 'findPathToClosestDot returned an illegal move: %s!\n%s' % t
|
||
|
|
currentState = currentState.generateSuccessor(0, action)
|
||
|
|
self.actionIndex = 0
|
||
|
|
print 'Path found with cost %d.' % len(self.actions)
|
||
|
|
|
||
|
|
def findPathToClosestDot(self, gameState):
|
||
|
|
"""
|
||
|
|
Returns a path (a list of actions) to the closest dot, starting from
|
||
|
|
gameState.
|
||
|
|
"""
|
||
|
|
# Here are some useful elements of the startState
|
||
|
|
startPosition = gameState.getPacmanPosition()
|
||
|
|
food = gameState.getFood()
|
||
|
|
walls = gameState.getWalls()
|
||
|
|
problem = AnyFoodSearchProblem(gameState)
|
||
|
|
|
||
|
|
"*** YOUR CODE HERE ***"
|
||
|
|
util.raiseNotDefined()
|
||
|
|
|
||
|
|
class AnyFoodSearchProblem(PositionSearchProblem):
|
||
|
|
"""
|
||
|
|
A search problem for finding a path to any food.
|
||
|
|
|
||
|
|
This search problem is just like the PositionSearchProblem, but has a
|
||
|
|
different goal test, which you need to fill in below. The state space and
|
||
|
|
successor function do not need to be changed.
|
||
|
|
|
||
|
|
The class definition above, AnyFoodSearchProblem(PositionSearchProblem),
|
||
|
|
inherits the methods of the PositionSearchProblem.
|
||
|
|
|
||
|
|
You can use this search problem to help you fill in the findPathToClosestDot
|
||
|
|
method.
|
||
|
|
"""
|
||
|
|
|
||
|
|
def __init__(self, gameState):
|
||
|
|
"Stores information from the gameState. You don't need to change this."
|
||
|
|
# Store the food for later reference
|
||
|
|
self.food = gameState.getFood()
|
||
|
|
|
||
|
|
# Store info for the PositionSearchProblem (no need to change this)
|
||
|
|
self.walls = gameState.getWalls()
|
||
|
|
self.startState = gameState.getPacmanPosition()
|
||
|
|
self.costFn = lambda x: 1
|
||
|
|
self._visited, self._visitedlist, self._expanded = {}, [], 0 # DO NOT CHANGE
|
||
|
|
|
||
|
|
def isGoalState(self, state):
|
||
|
|
"""
|
||
|
|
The state is Pacman's position. Fill this in with a goal test that will
|
||
|
|
complete the problem definition.
|
||
|
|
"""
|
||
|
|
x,y = state
|
||
|
|
|
||
|
|
"*** YOUR CODE HERE ***"
|
||
|
|
util.raiseNotDefined()
|
||
|
|
|
||
|
|
def mazeDistance(point1, point2, gameState):
|
||
|
|
"""
|
||
|
|
Returns the maze distance between any two points, using the search functions
|
||
|
|
you have already built. The gameState can be any game state -- Pacman's
|
||
|
|
position in that state is ignored.
|
||
|
|
|
||
|
|
Example usage: mazeDistance( (2,4), (5,6), gameState)
|
||
|
|
|
||
|
|
This might be a useful helper function for your ApproximateSearchAgent.
|
||
|
|
"""
|
||
|
|
x1, y1 = point1
|
||
|
|
x2, y2 = point2
|
||
|
|
walls = gameState.getWalls()
|
||
|
|
assert not walls[x1][y1], 'point1 is a wall: ' + str(point1)
|
||
|
|
assert not walls[x2][y2], 'point2 is a wall: ' + str(point2)
|
||
|
|
prob = PositionSearchProblem(gameState, start=point1, goal=point2, warn=False, visualize=False)
|
||
|
|
return len(search.bfs(prob))
|