June 2018 Update

Task/Rock-paper-scissors/Rust/rock-paper-scissors.rust

@@ -0,0 +1,83 @@
+extern crate rand;
+#[macro_use]
+extern crate rand_derive;
+
+use std::io;
+use rand::Rng;
+use Choice::*;
+
+#[derive(PartialEq, Clone, Copy, Rand, Debug)]
+enum Choice {
+    Rock,
+    Paper,
+    Scissors,
+}
+
+fn beats(c1: Choice, c2: Choice) -> bool {
+    (c1 == Rock && c2 == Scissors) || (c1 == Scissors && c2 == Paper) || (c1 == Paper && c2 == Rock)
+}
+
+fn ai_move<R: Rng>(rng: &mut R, v: [usize; 3]) -> Choice {
+    // weighted random choice, a dynamic version of `rand::distributions::WeightedChoice`
+    let rand = rng.gen_range(0, v[0] + v[1] + v[2]);
+    if rand < v[0] {
+        Paper
+    } else if rand < v[0] + v[1] {
+        Scissors
+    } else {
+        Rock
+    }
+}
+
+fn main() {
+    let mut rng = rand::thread_rng();
+
+    println!("Rock, paper, scissors!");
+    let mut ai_choice: Choice = rng.gen();
+    let mut ucf = [0, 0, 0]; // user choice frequency
+    let mut score = [0, 0];
+
+    loop {
+        println!("Please input your move: 'r', 'p' or 's'. Type 'q' to quit");
+
+        let mut input = String::new();
+        io::stdin()
+            .read_line(&mut input)
+            .expect("failed to read line");
+        let u_choice = match input.to_lowercase().trim() {
+            s if s.starts_with('r') => {
+                ucf[0] += 1;
+                Rock
+            }
+            s if s.starts_with('p') => {
+                ucf[1] += 1;
+                Paper
+            }
+            s if s.starts_with('s') => {
+                ucf[2] += 1;
+                Scissors
+            }
+            s if s.starts_with('q') => break,
+            _ => {
+                println!("Please enter a correct choice!");
+                continue;
+            }
+        };
+        println!("You chose {:?}, I chose {:?}.", u_choice, ai_choice);
+        if beats(u_choice, ai_choice) {
+            score[0] += 1;
+            println!("You win!");
+        } else if u_choice == ai_choice {
+            println!("It's a tie!");
+        } else {
+            score[1] += 1;
+            println!("I win!");
+        }
+        println!("-Score: You {}, Me {}", score[0], score[1]);
+
+        // only after the 1st iteration the AI knows the stats and can make
+        // its weighted random move
+        ai_choice = ai_move(&mut rng, ucf);
+    }
+    println!("Thank you for the game!");
+}