Finish course 4 assignment 3 TSP with heuristic

src/main.rs

@@ -12,6 +12,7 @@ mod mwis;
 mod prims;
 mod quick_sort;
 mod ssc;
+mod tsp;
 mod two_sum;
 mod util;
 
@@ -27,6 +28,7 @@ use crate::mwis::mwis;
 use crate::prims::prims;
 use crate::quick_sort::quick_sort;
 use crate::ssc::ssc;
+use crate::tsp::tsp_heuristic;
 use crate::two_sum::find_two_sums;
 use std::cmp::min;
 
@@ -163,12 +165,14 @@ fn c4a2() {
 
 #[allow(dead_code)]
 fn c4a3() {
-    println!("Continue here");
+    let g = util::read_tsp_graph("data/c4a3_tsp.txt").unwrap();
+    let r = tsp_heuristic(g);
+    println!("r = {}", r);
 }
 
 #[allow(dead_code)]
 fn c4a4() {
-    println!("we are done!");
+    println!("we are done soon!");
 }
 
 fn main() {

src/tsp.rs

@@ -0,0 +1,39 @@
+#[derive(Debug)]
+pub struct Graph {
+    pub n_nodes: usize,
+    pub nodes: Vec<Node>,
+}
+
+#[derive(Debug, Copy, Clone)]
+pub struct Node {
+    pub id: usize,
+    pub x: f64,
+    pub y: f64,
+}
+
+fn distance(a: &Node, b: &Node) -> f64 {
+    ((a.x - b.x).powf(2.0) + (a.y - b.y).powf(2.0)).sqrt()
+}
+
+pub fn tsp_heuristic(mut g: Graph) -> f64 {
+    let mut dist: f64 = 0.0;
+    let mut current_node = g.nodes.remove(0);
+    let first_node = current_node;
+
+    while g.nodes.len() > 0 {
+        let mut min_dist = f64::MAX;
+        let mut min_id = 0;
+        for i in 0..g.nodes.len() {
+            let node = &g.nodes[i];
+            let new_dist = distance(node, &current_node);
+            if new_dist < min_dist {
+                min_dist = new_dist;
+                min_id = i;
+            }
+        }
+        current_node = g.nodes.remove(min_id);
+        dist += min_dist;
+    }
+    dist += distance(&current_node, &first_node);
+    dist
+}

src/util.rs

@@ -8,6 +8,7 @@ use crate::min_cut;
 use crate::mwis;
 use crate::prims;
 use crate::ssc;
+use crate::tsp;
 use std::fs::File;
 use std::io;
 use std::io::{BufRead, BufReader, Error, ErrorKind};
@@ -353,3 +354,31 @@ pub fn read_floyd_warshall_graph(path: &str) -> Result<floyd_warshall::Graph, io
 
     Ok(g)
 }
+
+pub fn read_tsp_graph(path: &str) -> Result<tsp::Graph, io::Error> {
+    let file = File::open(path)?;
+    let mut lines = BufReader::new(file).lines();
+    let line = lines.next().unwrap()?;
+    let n_nodes = line.parse().unwrap();
+
+    let mut g = tsp::Graph {
+        n_nodes: n_nodes,
+        nodes: Vec::new(),
+    };
+
+    for line in lines {
+        let line = line?;
+        let mut it = line.split_whitespace();
+        let node_id: usize = it.next().unwrap().parse().unwrap();
+        let x = it.next().unwrap().parse().unwrap();
+        let y = it.next().unwrap().parse().unwrap();
+        let n = tsp::Node {
+            id: node_id - 1,
+            x: x,
+            y: y,
+        };
+        g.nodes.push(n);
+    }
+
+    Ok(g)
+}