力扣-232题用栈实现队列（C++）

旧城等待， 2022-08-31 04:42 178阅读 0赞

题目链接：[https://leetcode-cn.com/problems/implement-queue-using-stacks/][https_leetcode-cn.com_problems_implement-queue-using-stacks]  
题目如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70 1]

class MyQueue {
        
    public:
        stack<int> stk1;
        stack<int> stk2;
        /** Initialize your data structure here. */
        MyQueue() {
        
            
        }
        
        /** Push element x to the back of queue. */
        void push(int x) {
        
            //将元素压入堆栈stk1
            stk1.push(x);
        }
        
        /** Removes the element from in front of queue and returns that element. */
        int pop() {
        
            //将元素放到stk2，拿到最先放入stk1的元素，并移除，再放回stk1
            int num;
            while(!stk1.empty()){
        
                num=stk1.top();
                stk1.pop();
                stk2.push(num);
            }
            num=stk2.top();
            stk2.pop();
    
            int num1;
            while(!stk2.empty()){
        
                num1=stk2.top();
                stk2.pop();
                stk1.push(num1);
            }
    
            return num;
    
        }
        
        /** Get the front element. */
        int peek() {
        
            //将元素依次放到stk2，拿到最后一个出栈的元素，再还原回去
            int num;
            while(!stk1.empty()){
        
                num=stk1.top();
                stk1.pop();
                stk2.push(num);
            }
    
            int num1;
            while(!stk2.empty()){
        
                num1=stk2.top();
                stk2.pop();
                stk1.push(num1);
            }
    
            return num;
    
        }
        
        /** Returns whether the queue is empty. */
        bool empty() {
        
            return stk1.empty()&&stk2.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();
     */

[https_leetcode-cn.com_problems_implement-queue-using-stacks]: https://leetcode-cn.com/problems/implement-queue-using-stacks/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70]: /images/20220829/778f9b97a535410e9630b40901eb6acb.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70 1]: /images/20220829/4d638de73e36480d8f583a1fb348ebc9.png