Solve 2024 day 21 to finish the year

2024/d21.py

@@ -1,25 +1,29 @@
-import heapq
 from lib import get_data
+from collections import deque
+from functools import cache
 
 
 data = get_data(__file__)
+# data = """029A
+# 980A
+# 179A
+# 456A
+# 379A"""
 
 
 def new_dir(current, move):
-    return {"<": 
+    return {
-                {">": "v"},
+        "<": {">": "v"},
-            "^":
+        "^": {">": "A", "v": "v"},
-                {">": "A", "v": "v"},
+        "v": {"<": "<", ">": ">", "^": "^"},
-            "v":
+        ">": {"^": "A", "<": "v"},
-                {"<": "<", ">": ">", "^": "^"},
+        "A": {"<": "^", "v": ">"},
-            ">":
-                {"^": "A", "<": "v"},
-            "A":
-                {"<": "^", "v": ">"}
     }[current].get(move, None)
 
+
 def new_num(current, move):
-    return {"7": {">": "8", "v": "4",},
+    return {
+        "7": {">": "8", "v": "4", },
         "8": {"<": "7", ">": "9", "v": "5"},
         "9": {"<": "8", "v": "6"},
         "4": {"^": "7", ">": "5", "v": "1"},
@@ -33,111 +37,51 @@ def new_num(current, move):
     }[current].get(move, None)
 
 
-def new_state(press, node, has_numpad):
+@cache
-    key_pads, num_pad, typed, pressed = node
+def find(code, depth, lookup):
-    key_pads = list(key_pads)
+    if depth == 0:
-    pressed = pressed + press
+        return len(code)
-
+    code = list(code)
-    for i in range(len(key_pads)):
-        if press == "A":
-            press = key_pads[i]
-        else:
-            key_pads[i] = new_dir(key_pads[i], press)
-            if key_pads[i] is None:
-                return None
-            press = None
-            break
-
-    if press is not None:
-        if has_numpad:
-            if press == "A":
-                typed = typed + num_pad
-            else:
-                num_pad = new_num(num_pad, press)
-                if num_pad is None:
-                    return None
-        else:
-            typed = typed + press
-    nnode = tuple(key_pads), num_pad, typed, pressed
-    return nnode
-
-    # if press == "A":
-    #     if key_pads[0] == "A":
-    #         if key_pads[1] == "A":
-    #             entered += num_pad
-    #         else:
-    #             num_pad = new_num(num_pad, key_pads[1])
-    #     else:
-    #         key_pads[1] = new_dir(key_pads[1], key_pads[0])
-    # else:
-    #     key_pads[0] = new_dir(key_pads[0], press)
-    #
-    # if key_pads[0] is None or key_pads[1] is None or num_pad is None:
-    #     return None
-    # return tuple(key_pads), num_pad, typed
-
-def find(code, key_pads=2, has_numpad=False):
-    _, _, TYPED, ENTERED = 0, 1, 2, 3
-
-    def dist(n1, n2):
-        if n1 == 0: return 0
-        return 1
-
-    def h(node):
-        return len(code) - len(node[TYPED])
-
-    def is_goal(node):
-        return node[TYPED] == code
-
-    def neighbors(node):
-        nbs = []
-        for move in '<^v>A':
-            nb = new_state(move, node, has_numpad)
-            if nb is None:
-                continue
-            if not code.startswith(nb[TYPED]):
-                continue
-            nbs.append(nb)
-        return nbs
-
-    def hash(node):
-        return node[:-1]
-
-    key_pads = tuple(['A' for _ in range(key_pads)])
-    start = (key_pads, 'A', '', '')
-    starts = [start]
-    open_set = []
-    g_score = {}
-    cost = None
-
-    for start in starts:
-        heapq.heappush(open_set, (h(start), start))
-        g_score[hash(start)] = dist(0, start)
-
-    while open_set:
-        current_f_score, current = heapq.heappop(open_set)
-        if is_goal(current):
-            assert current_f_score == g_score[hash(current)]
-            # print(current)
-            cost = g_score[hash(current)]
-            cost = current[ENTERED]
-            break
-
-        # print(current)
-        for neighbor in neighbors(current):
-            tentative_g_score = g_score[hash(current)] + dist(current, neighbor)
-            if tentative_g_score < g_score.get(hash(neighbor), 10**15):
-                # print("  ", neighbor, end="")
-                # input()
-                g_score[hash(neighbor)] = tentative_g_score
-                f_score = g_score[hash(neighbor)] + h(neighbor)
-                heapq.heappush(open_set, (f_score, neighbor))
-    return cost
-
     t = 0
+    current = "A"
+    while code:
+        solutions = []
+        target = code.pop(0)
+        start = (current, "")
+        seen = set()
+        queue = deque([start])
+        while queue:
+            node = queue.popleft()
+            if node in seen:
+                continue
+            seen.add(node)
+            if node[0] == target:
+                solution = node[1] + "A"
+                if len(solutions) == 0:
+                    solutions.append(solution)
+                elif len(solutions[-1]) == len(solution):
+                    solutions.append(solution)
+                else:
+                    break
+                continue
+
+            for c in "<>v^":
+                next = lookup(node[0], c)
+                if next is not None:
+                    queue.append((next, node[1] + c))
+        current = target
+        t += min(find(code, depth - 1, new_dir) for code in solutions)
+    return t
+
+
+p1, p2 = 0, 0
 for line in data.splitlines():
-    s = find(line, 2, True)
     i = int("".join([c for c in line if c.isdigit()]))
-    s = len(s)
+    s1 = find(line, 3, new_num)
-    t += s * i
+    s2 = find(line, 26, new_num)
-print(t)
+    p1 += s1 * i
+    p2 += s2 * i
+
+
+print(p1)
+print(p2)

README.md

@@ -311,9 +311,9 @@ and focus. Of course, learning more algorithms and techniques helps.
 - Day 18: `14:35:01 20398      0   14:37:18  19550      0`
 - Day 19: `00:14:37  2001      0   00:19:43   1584      0`
 - Day 20: `01:08:53  3637      0   01:53:01   2837      0`
-- Day 21: `00:48:40   215      0          -      -      -`
+- Day 21: `00:48:40   215      0       >24h  16427      0`
 - Day 22: `00:13:04  1930      0   00:28:29    739      0`
 - Day 23: `   >24h  20096      0       >24h  17620      0`
 - Day 24: `15:57:01 17307      0       >24h  11326      0`
-- Day 25: `10:41:54 14140      0          -      -      -`
+- Day 25: `10:41:54 14140      0       >24h  13631      0`