算法入门：队列实现堆栈，堆栈实现队列

leetcode232：两个堆栈实现队列

class MyQueue {
private:
    stack a;
    stack b;
public:
    /** Initialize your data structure here. */
    MyQueue():a(),b() {
        
    }
    
    /** Push element x to the back of queue. */
    void push(int x) {
        a.push(x);
    }
    
    /** Removes the element from in front of queue and returns that element. */
    int pop() {
        if(b.empty()){
            while(!a.empty()){
                b.push(a.top());
                a.pop();
            }
        }
        int temp=b.top();
        b.pop();
        return temp;
    }
    
    /** Get the front element. */
    int peek() {
        if(b.empty()){
            while(!a.empty()){
                b.push(a.top());
                a.pop();
            }
        }
        return b.top();
    }
    
    /** Returns whether the queue is empty. */
    bool empty() {
        return b.empty() && a.empty();
    }
};

leetcode225：两个队列实现堆栈

class MyStack {
private:
    queue a;
    queue b;
public:
    /** Initialize your data structure here. */
    MyStack():a(),b() {
        
    }
    
    /** Push element x onto stack. */
    void push(int x) {
        a.push(x);
    }
    
    /** Removes the element on top of the stack and returns that element. */
    int pop() {
        int temp;
        while(!a.empty()){
            temp=a.front();
            a.pop();
            if(!a.empty())
                b.push(temp);
        }
        while(!b.empty()){
            a.push(b.front());
            b.pop();
        }
        return temp;        
    }
    
    /** Get the top element. */
    int top() {
        int temp;
        while(!a.empty()){
            temp=a.front();
            a.pop();
            b.push(temp);
        }
        while(!b.empty()){
            a.push(b.front());
            b.pop();
        }
        return temp; 
    }
    
    /** Returns whether the stack is empty. */
    bool empty() {
        return a.empty()&&b.empty();
    }
};