add dijkstra's algorithm in rust (#294)

Author: hackeryarn

09_dijkstras_algorithm/rust/Cargo.lock

@@ -0,0 +1,6 @@
+[package]
+name = "dijkstra"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

09_dijkstras_algorithm/rust/Cargo.toml

@@ -0,0 +1,70 @@
+use std::{collections::HashMap, u64};
+
+fn find_lowest_cost_node(processed: &Vec<String>, costs: &HashMap<String, u64>) -> Option<String> {
+    let mut lowest_cost = u64::MAX;
+    let mut lowest_cost_node = None;
+    for (node, cost) in costs.iter() {
+        if *cost < lowest_cost && !processed.contains(node) {
+            lowest_cost = *cost;
+            lowest_cost_node = Some(node);
+        }
+    }
+    return lowest_cost_node.cloned();
+}
+
+fn main() {
+    // Graph Setup
+    let mut graph = HashMap::new();
+
+    let mut start_edges: HashMap<String, u64> = HashMap::new();
+    start_edges.insert("a".to_string(), 6);
+    start_edges.insert("b".to_string(), 2);
+    graph.insert("start".to_string(), start_edges);
+
+    let mut a_edges = HashMap::new();
+    a_edges.insert("fin".to_string(), 1);
+    graph.insert("a".to_string(), a_edges);
+
+    let mut b_edges = HashMap::new();
+    b_edges.insert("a".to_string(), 3);
+    b_edges.insert("fin".to_string(), 5);
+    graph.insert("b".to_string(), b_edges);
+
+    let fin_edges = HashMap::new();
+    graph.insert("fin".to_string(), fin_edges);
+
+    // Costs Setup
+    let mut costs: HashMap<String, u64> = HashMap::new();
+    costs.insert("a".to_string(), 6);
+    costs.insert("b".to_string(), 2);
+    costs.insert("fin".to_string(), u64::MAX);
+
+    // Parents Setup
+    let mut parents = HashMap::new();
+    parents.insert("a".to_string(), Some("start".to_string()));
+    parents.insert("b".to_string(), Some("start".to_string()));
+    parents.insert("fin".to_string(), None);
+
+    let mut processed: Vec<String> = vec![];
+
+    loop {
+        let node = find_lowest_cost_node(&processed, &costs);
+        match node {
+            Some(node) => {
+                let cost = *costs.get(&node).unwrap();
+                let neighbors = graph.get(&node).unwrap();
+                for (n, ncost) in neighbors.iter() {
+                    let new_cost = cost + *ncost;
+                    if *costs.get(n).unwrap() > new_cost {
+                        costs.insert(n.to_string(), new_cost);
+                        parents.insert(n.to_string(), Some(node.clone()));
+                    }
+                }
+                processed.push(node)
+            }
+            None => break,
+        }
+    }
+    println!("costs: {:?}", costs);
+    println!("parents: {:?}", parents);
+}