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,

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)]
@@ -143,8 +144,20 @@ fn c3a4() {
 }
 
 #[allow(dead_code)]
-fn c4a4() {
-	println!("Final course!");
+fn c4a1() {
+    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();
-    c4a4();
+    // c3a4();
+    // c4a1();
+    c4a2();
 }

src/mwis.rs

@@ -1,4 +1,3 @@
-
 #[derive(Debug)]
 pub struct IndependentSet {
     pub length: usize,
@@ -14,7 +13,6 @@ struct Solution {
 pub fn mwis(s: &IndependentSet) -> Vec<usize> {
     let mut solutions: Vec<Solution> = Vec::new();
 
-
     solutions.push(Solution {
         weight: s.weights[0],
         nodes: vec![0],
@@ -43,7 +41,6 @@ pub fn mwis(s: &IndependentSet) -> Vec<usize> {
         } else {
             solutions.push(s2);
         }
-
     }
 
     let solution = solutions.pop().unwrap();

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)
+}