leetcode 232 用栈实现队列

简介

使用队列实现队列哈哈.

code

class MyQueue {
public:
    queue<int> q;
public:
    /** Initialize your data structure here. */
    MyQueue() {
        
    }
    
    /** Push element x to the back of queue. */
    void push(int x) {
        return q.push(x);
    }
    
    /** Removes the element from in front of queue and returns that element. */
    int pop() {
        int a = q.front();
        q.pop();
        return a;
    }
    
    /** Get the front element. */
    int peek() {
        return q.front();
    }
    
    /** Returns whether the queue is empty. */
    bool empty() {
        return q.empty();
    }
};

/**
 * Your MyQueue object will be instantiated and called as such:
 * MyQueue* obj = new MyQueue();
 * obj->push(x);
 * int param_2 = obj->pop();
 * int param_3 = obj->peek();
 * bool param_4 = obj->empty();
 */

class MyQueue {
    Stack<Integer> stacka;
    Stack<Integer> stackb;
    /** Initialize your data structure here. */
    public MyQueue() {
        stacka = new Stack<>();
        stackb = new Stack<>();
    }
    
    /** Push element x to the back of queue. */
    public void push(int x) {
        stacka.push(x);
    }
    
    /** Removes the element from in front of queue and returns that element. */
    public int pop() {
        if(stackb.isEmpty()){
            while(!stacka.isEmpty()) {
                stackb.push(stacka.pop());
            }
        }
        return stackb.pop();
    }
    
    /** Get the front element. */
    public int peek() {
        if(stackb.isEmpty()){
            while(!stacka.isEmpty()){
                stackb.push(stacka.pop());
            }
        }
        return stackb.peek();
    }
    
    /** Returns whether the queue is empty. */
    public boolean empty() {
        return stackb.isEmpty() && stacka.isEmpty();
    }
}

/**
 * Your MyQueue object will be instantiated and called as such:
 * MyQueue obj = new MyQueue();
 * obj.push(x);
 * int param_2 = obj.pop();
 * int param_3 = obj.peek();
 * boolean param_4 = obj.empty();
 */