leetcode刷题09--用栈实现队列--T232

题目:

image.png

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思路:

可以说很简单了,参考一下225的题解,就能想到,使用一个中间栈.
让栈的存放顺序和队列一致,这样pop操作和front操作就不用进行修改,唯一需要改动的也只有push操作:
先将原栈的数据push到tem栈中,然后将新的元素push到tem中,最后将tem栈的数据push到原栈中,就完成了顺序的保持.

见图:

image.png

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代码:

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

/**
 * 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();
 */

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总结:
终于自己想出一道题目了,还是很欣慰的,有效思考大于被动学习.
加油!