add greedy algorithms example in rust (#295)

10_greedy_algorithms/rust/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "greedy_algorithms"
+version = "0.1.0"

10_greedy_algorithms/rust/Cargo.toml

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

10_greedy_algorithms/rust/src/main.rs

@@ -0,0 +1,42 @@
+use std::collections::{HashMap, HashSet};
+
+fn main() {
+    let mut states_needed = HashSet::from(["mt", "wa", "or", "id", "nv", "ut", "ca", "az"]);
+
+    let mut stations = HashMap::from([
+        ("kone", HashSet::from(["id", "nv", "ut"])),
+        ("ktwo", HashSet::from(["wa", "id", "mt"])),
+        ("kthree", HashSet::from(["or", "nv", "ca"])),
+        ("kfour", HashSet::from(["nv", "ut"])),
+        ("kfive", HashSet::from(["ca", "az"])),
+    ]);
+
+    let mut final_stations = HashSet::new();
+    while !states_needed.is_empty() {
+        let mut best_station = None;
+        let mut states_covered = HashSet::new();
+        for (station, states_for_station) in &stations {
+            let covered: HashSet<_> = states_needed
+                .intersection(&states_for_station)
+                .cloned()
+                .collect();
+            if covered.len() > states_covered.len() && !final_stations.contains(station) {
+                best_station = Some(*station);
+                states_covered = covered;
+            }
+        }
+        match best_station {
+            Some(station) => {
+                states_needed = states_needed.difference(&states_covered).cloned().collect();
+                final_stations.insert(station);
+                stations.remove(station);
+            }
+            None => {
+                println!("Coold not complete: {:?}", final_stations);
+                break;
+            }
+        }
+    }
+
+    println!("{:?}", final_stations);
+}