剑指offer.用两个栈实现队列

class MyQueue {
public:
    /** Initialize your data structure here. */
    stack<int> stack1,stack2;
    MyQueue() {
        
    }
    
    /** Push element x to the back of queue. */
    void push(int x) {
        stack1.push(x);
    }
    void copy(stack<int> &a, stack<int>& b){
        while(a.size()){
            b.push(a.top());
            a.pop();
        }
    }
    /** Removes the element from in front of queue and returns that element. */
    int pop() {
        copy(stack1, stack2);
            int result = stack2.top();
            stack2.pop();
copy(stack2,stack1);
        return result;
        
    }
    
    /** Get the front element. */
    int peek() {
        copy(stack1, stack2);
        int result = stack2.top();
        copy(stack2,stack1);
        return result;
    }
    
    /** Returns whether the queue is empty. */
    bool empty() {
        return stack1.empty();
    }
};

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