Solution.rs

use std::collections::VecDeque;

struct MyQueue {
    stk1: Vec<i32>,
    stk2: Vec<i32>,
}

impl MyQueue {
    fn new() -> Self {
        MyQueue {
            stk1: Vec::new(),
            stk2: Vec::new(),
        }
    }

    fn push(&mut self, x: i32) {
        self.stk1.push(x);
    }

    fn pop(&mut self) -> i32 {
        self.move_elements();
        self.stk2.pop().unwrap()
    }

    fn peek(&mut self) -> i32 {
        self.move_elements();
        *self.stk2.last().unwrap()
    }

    fn empty(&self) -> bool {
        self.stk1.is_empty() && self.stk2.is_empty()
    }

    fn move_elements(&mut self) {
        if self.stk2.is_empty() {
            while let Some(element) = self.stk1.pop() {
                self.stk2.push(element);
            }
        }
    }
}/**
 * Your MyQueue object will be instantiated and called as such:
 * let obj = MyQueue::new();
 * obj.push(x);
 * let ret_2: i32 = obj.pop();
 * let ret_3: i32 = obj.peek();
 * let ret_4: bool = obj.empty();
 */