Implement floyd-warshall algorithm for course 4 assignment 1

src/floyd_warshall.rs

@@ -0,0 +1,77 @@
+use std::cmp::min;
+
+#[derive(Debug)]
+pub struct Graph {
+    pub n_nodes: usize,
+    pub n_edges: usize,
+    pub nodes: Vec<Node>,
+}
+
+#[derive(Debug)]
+pub struct Node {
+    pub id: usize,
+    pub edges: Vec<Edge>,
+}
+
+#[derive(Debug)]
+pub struct Edge {
+    pub source: usize,
+    pub target: usize,
+    pub length: i64,
+}
+
+pub fn floyd_warshall(g: Graph) -> Option<i64> {
+	let n = g.n_nodes;
+    let mut a: Vec<Vec<i64>> = vec![vec![std::i64::MAX; n]; n];
+
+    // nodes have lengths of 0 to themself
+    for i in 0..n {
+    	a[i][i] = 0;
+    }
+
+    // nodes that are connected get the length of their edge
+    for n in &g.nodes {
+    	for e in &n.edges {
+    		a[e.source][e.target] = e.length;
+    	}
+    }
+
+    // main workloop
+    for k in 0..n {
+    	let mut new_a = a.to_vec();
+    	for i in 0..n {
+    		for j in 0..n {
+    			let case_1 = a[i][j];
+    			let case_2 = match a[i][k].checked_add(a[k][j]) {
+    				Some(v) => v,
+    				None => std::i64::MAX,
+    			};
+
+    			new_a[i][j] = min(case_1, case_2);
+    		}
+    	} 
+    	a = new_a;
+    }
+
+    // node to itself is negative means we have negative cost cycles
+    for i in 0..n {
+    	if a[i][i] < 0 {
+    		return None;
+    	}
+    }
+
+    // find min path from v to u
+    let mut r = std::i64::MAX;
+    for i in 0..n {
+    	for j in 0..n {
+    		if i != j {
+	    		let d = a[i][j];
+	    		if d < r {
+	    			r = d;
+	    		}
+    		}
+    	}
+    }
+
+    Some(r)
+}

src/knapsack.rs

@@ -1,4 +1,3 @@
-
 #[derive(Debug)]
 pub struct Knapsack {
     pub size: usize,
@@ -8,26 +7,26 @@ pub struct Knapsack {
 
 #[derive(Debug)]
 pub struct Item {
-	pub value: usize,
+    pub value: usize,
-	pub weight: usize,
+    pub weight: usize,
 }
 
 pub fn knapsack(k: &Knapsack) -> usize {
-	let mut weight_to_value = vec![0; k.size];
+    let mut weight_to_value = vec![0; k.size];
-	for item_index in 0..k.n_items {
+    for item_index in 0..k.n_items {
-		let mut new_weight_to_value = weight_to_value.to_vec();
+        let mut new_weight_to_value = weight_to_value.to_vec();
-		let item = &k.items[item_index];
+        let item = &k.items[item_index];
-		for weight in 0..k.size {
+        for weight in 0..k.size {
-			if weight >= item.weight {
+            if weight >= item.weight {
-				let current_value = weight_to_value[weight];
+                let current_value = weight_to_value[weight];
-				let new_value = weight_to_value[weight - item.weight] + item.value;
+                let new_value = weight_to_value[weight - item.weight] + item.value;
-				if new_value > current_value {
+                if new_value > current_value {
-					new_weight_to_value[weight] = new_value;
+                    new_weight_to_value[weight] = new_value;
-				}
+                }
-			}
+            }
-		}
+        }
-		weight_to_value = new_weight_to_value;
+        weight_to_value = new_weight_to_value;
-	}
+    }
 
-	weight_to_value.pop().unwrap()
+    weight_to_value.pop().unwrap()
 }

src/main.rs

@@ -1,32 +1,33 @@
 mod dijkstra;
+mod floyd_warshall;
 mod heap;
 mod huffman;
 mod jobs;
 mod k_clustering;
 mod k_clustering_big;
-mod mwis;
+mod knapsack;
 mod merge_sort;
 mod min_cut;
+mod mwis;
 mod prims;
 mod quick_sort;
 mod ssc;
 mod two_sum;
 mod util;
-mod knapsack;
 
 use crate::dijkstra::dijkstra;
 use crate::heap::heap;
 use crate::jobs::{jobs_1, jobs_2};
 use crate::k_clustering::k_clustering;
 use crate::k_clustering_big::k_clustering_big;
+use crate::knapsack::knapsack;
 use crate::merge_sort::merge_sort_inversions;
 use crate::min_cut::min_cut;
+use crate::mwis::mwis;
 use crate::prims::prims;
 use crate::quick_sort::quick_sort;
 use crate::ssc::ssc;
 use crate::two_sum::find_two_sums;
-use crate::mwis::mwis;
-use crate::knapsack::knapsack;
 use std::cmp::min;
 
 #[allow(dead_code)]
@@ -133,18 +134,30 @@ fn c3a3() {
 
 #[allow(dead_code)]
 fn c3a4() {
-	let k1 = util::read_knapsack("data/c3a4_knapsack1.txt").unwrap();
+    let k1 = util::read_knapsack("data/c3a4_knapsack1.txt").unwrap();
-	let r1 = knapsack::knapsack(&k1);
+    let r1 = knapsack::knapsack(&k1);
 
-	let k2 = util::read_knapsack("data/c3a4_knapsack_big.txt").unwrap();
+    let k2 = util::read_knapsack("data/c3a4_knapsack_big.txt").unwrap();
-	let r2 = knapsack::knapsack(&k2);
+    let r2 = knapsack::knapsack(&k2);
-	println!("r1 = {} r2 = {}", r1, r2);
+    println!("r1 = {} r2 = {}", r1, r2);
-	// r1 = 2493893 r2 = 4243395
+    // r1 = 2493893 r2 = 4243395
 }
 
 #[allow(dead_code)]
-fn c4a4() {
+fn c4a1() {
-	println!("Final course!");
+    let g1 = util::read_floyd_warshall_graph("data/c4a1_g1.txt").unwrap();
+    let r1 = floyd_warshall::floyd_warshall(g1);
+    let g2 = util::read_floyd_warshall_graph("data/c4a1_g2.txt").unwrap();
+    let r2 = floyd_warshall::floyd_warshall(g2);
+    let g3 = util::read_floyd_warshall_graph("data/c4a1_g3.txt").unwrap();
+    let r3 = floyd_warshall::floyd_warshall(g3);
+    println!("r1 = {:?} r2 = {:?} r3 = {:?}", r1, r2, r3);
+    // r = -19
+}
+
+#[allow(dead_code)]
+fn c4a2() {
+	println!("continue here");
 }
 
 fn main() {
@@ -158,6 +171,7 @@ fn main() {
     // c3a1();
     // c3a2();
     // c3a3();
-    c3a4();
+    // c3a4();
-    c4a4();
+    // c4a1();
+    c4a2();
 }

src/mwis.rs

@@ -1,4 +1,3 @@
-
 #[derive(Debug)]
 pub struct IndependentSet {
     pub length: usize,
@@ -7,54 +6,52 @@ pub struct IndependentSet {
 
 #[derive(Debug)]
 struct Solution {
-	weight: u64,
+    weight: u64,
-	nodes: Vec<usize>,
+    nodes: Vec<usize>,
 }
 
 pub fn mwis(s: &IndependentSet) -> Vec<usize> {
-	let mut solutions: Vec<Solution> = Vec::new();
+    let mut solutions: Vec<Solution> = Vec::new();
 
+    solutions.push(Solution {
+        weight: s.weights[0],
+        nodes: vec![0],
+    });
 
-	solutions.push(Solution {
+    solutions.push(Solution {
-		weight: s.weights[0],
+        weight: s.weights[1],
-		nodes: vec![0],
+        nodes: vec![1],
-	});
+    });
 
-	solutions.push(Solution {
+    for i in 2..s.weights.len() {
-		weight: s.weights[1],
+        let s1 = Solution {
-		nodes: vec![1],
+            weight: solutions[i - 1].weight,
-	});
+            nodes: solutions[i - 1].nodes.to_vec(),
+        };
 
-	for i in 2..s.weights.len() {
+        let mut s2_vec = solutions[i - 2].nodes.to_vec();
-		let s1 = Solution {
+        s2_vec.push(i);
-			weight: solutions[i - 1].weight,
+        let s2 = Solution {
-			nodes: solutions[i - 1].nodes.to_vec(),
+            weight: solutions[i - 2].weight + s.weights[i],
-		};
+            nodes: s2_vec,
+        };
 
-		let mut s2_vec = solutions[i - 2].nodes.to_vec();
+        if s1.weight > s2.weight {
-		s2_vec.push(i);
+            solutions.push(s1);
-		let s2 = Solution {
+        } else {
-			weight: solutions[i - 2].weight + s.weights[i],
+            solutions.push(s2);
-			nodes: s2_vec,
+        }
-		};
+    }
 
-		if s1.weight > s2.weight {
+    let solution = solutions.pop().unwrap();
-			solutions.push(s1);
+    let mut result = Vec::new();
-		} else {
+    let vertices = vec![0, 1, 2, 3, 16, 116, 516, 996];
-			solutions.push(s2);
+    for v in &vertices {
-		}
+        if solution.nodes.contains(v) {
-
+            result.push(1);
-	}
+        } else {
-
+            result.push(0);
-	let solution = solutions.pop().unwrap();
+        }
-	let mut result = Vec::new();
+    }
-	let vertices = vec![0, 1, 2, 3, 16, 116, 516, 996];
+    result
-	for v in &vertices {
-		if solution.nodes.contains(v) {
-			result.push(1);
-		} else {
-			result.push(0);
-		}
-	}
-	result
 }

src/util.rs

@@ -1,12 +1,13 @@
+use crate::floyd_warshall;
 use crate::huffman;
 use crate::jobs;
 use crate::k_clustering;
 use crate::k_clustering_big;
+use crate::knapsack;
 use crate::min_cut;
+use crate::mwis;
 use crate::prims;
 use crate::ssc;
-use crate::mwis;
-use crate::knapsack;
 use std::fs::File;
 use std::io;
 use std::io::{BufRead, BufReader, Error, ErrorKind};
@@ -310,3 +311,45 @@ pub fn read_knapsack(path: &str) -> Result<knapsack::Knapsack, io::Error> {
 
     Ok(k)
 }
+
+pub fn read_floyd_warshall_graph(path: &str) -> Result<floyd_warshall::Graph, io::Error> {
+    let file = File::open(path)?;
+    let mut lines = BufReader::new(file).lines();
+    let line = lines.next().unwrap()?;
+    let mut fields = line.split_whitespace();
+    let n_nodes = fields.next().unwrap().parse().unwrap();
+    let n_edges = fields.next().unwrap().parse().unwrap();
+
+    let mut g = floyd_warshall::Graph {
+        n_nodes: n_nodes,
+        n_edges: n_edges,
+        nodes: Vec::new(),
+    };
+
+    for i in 0..n_nodes {
+        let n = floyd_warshall::Node {
+            id: i,
+            edges: Vec::new(),
+        };
+        g.nodes.push(n);
+    }
+
+    for line in lines {
+        let line = line?;
+        let mut it = line.split_whitespace();
+        let mut source = it.next().unwrap().parse().unwrap();
+        let mut target = it.next().unwrap().parse().unwrap();
+        let length = it.next().unwrap().parse().unwrap();
+        source = source - 1;
+        target = target - 1;
+
+        let e = floyd_warshall::Edge {
+            source: source,
+            target: target,
+            length: length,
+        };
+        g.nodes[source].edges.push(e);
+    }
+
+    Ok(g)
+}