add rust breadth first search (#293)

Author: hackeryarn

06_breadth-first_search/rust/Cargo.lock

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

06_breadth-first_search/rust/Cargo.toml

@@ -0,0 +1,68 @@
+use std::collections::{HashMap, VecDeque};
+use std::fmt;
+
+#[derive(Eq, Hash, PartialEq)]
+struct Person(String);
+
+impl Person {
+    fn is_seller(&self) -> bool {
+        self.0.ends_with('m')
+    }
+}
+
+impl fmt::Display for Person {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str(&self.0)
+    }
+}
+
+fn search(graph: &HashMap<&Person, Vec<&Person>>, start: &Person) {
+    let mut search_queue = VecDeque::new();
+    search_queue.push_back(start);
+
+    let mut searched: Vec<&Person> = Vec::with_capacity(graph.len());
+    loop {
+        match search_queue.pop_front() {
+            Some(person) => {
+                if !searched.contains(&person) {
+                    if person.is_seller() {
+                        println!("{} is a mango seller!", person);
+                        break;
+                    } else {
+                        for p in graph.get(&person).unwrap() {
+                            search_queue.push_back(p);
+                            searched.push(person);
+                        }
+                    }
+                }
+            }
+            None => {
+                println!("no mango seller found!");
+                break;
+            }
+        }
+    }
+}
+
+fn main() {
+    let you = Person("you".to_string());
+    let alice = Person("alice".to_string());
+    let bob = Person("bob".to_string());
+    let claire = Person("claire".to_string());
+    let anuj = Person("anuj".to_string());
+    let peggy = Person("peggy".to_string());
+    let thom = Person("thom".to_string());
+    let jonny = Person("jonny".to_string());
+
+    let mut graph = HashMap::new();
+    graph.insert(&you, vec![&alice, &bob, &claire]);
+    graph.insert(&bob, vec![&anuj, &peggy]);
+    graph.insert(&alice, vec![&peggy]);
+    graph.insert(&claire, vec![&thom, &jonny]);
+    graph.insert(&anuj, vec![]);
+    graph.insert(&peggy, vec![]);
+    graph.insert(&thom, vec![]);
+    graph.insert(&jonny, vec![]);
+
+    search(&graph, &you);
+}