Come from : [https://leetcode-cn.com/problems/implement-stack-using-queues/submissions/]
232. Implement Queue using Stacks
1.Question
Implement the following operations of a queue using stacks.
push(x) – Push element x to the back of queue.
pop() – Removes the element from in front of queue.
peek() – Get the front element.
empty() – Return whether the queue is empty.
Notes:
1. You must use only standard operations of a stack -- which means only push to top, peek/pop from top, size, and is empty operations are valid.
2. Depending on your language, stack may not be supported natively. You may simulate a stack by using a list or deque (double-ended queue), as long as you use only standard operations of a stack.
3. You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).
Example :
MyQueue queue = new MyQueue();
queue.push(1);
queue.push(2);
queue.peek(); // returns 1
queue.pop(); // returns 1
queue.empty(); // returns false
2.Answer
easy 类型题目。.不多BB（和前天的 101.用队列实现栈类似）。
AC代码如下：
class MyQueue {
public:
/** Initialize your data structure here. */
MyQueue() {
}
/** Push element x to the back of queue. */
void push(int x) {
while(!data.empty())
{
temp.push(data.top());
data.pop();
}
temp.push(x);
while(!temp.empty())
{
data.push(temp.top());
temp.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:
stack<int> temp;
stack<int> 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();
*/
3.我的收获
栈，队列。。。
fighting。。。
2019/6/18 胡云层 于南京 103