AcWing 20. 用两个栈实现队列
原题链接
简单
作者:
我要出去乱说
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2021-01-26 11:03:25
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所有人可见
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阅读 507
class MyQueue {
public:
/** Initialize your data structure here. */
stack<int> s1, s2; //定义两个栈,用来模拟队列
MyQueue() {
}
/** Push element x to the back of queue. */
void push(int x) {
s1.push(x); //s1用于储存,s2用于缓存
}
/** Removes the element from in front of queue and returns that element. */
int pop() { //把栈1除了栈顶之外的元素移到栈2,弹出栈1的栈顶元素后再将其他元素从栈2还原
while (s1.size() > 1) s2.push(s1.top()), s1.pop();
int t = s1.top();
s1.pop();
while (s2.size()) s1.push(s2.top()), s2.pop();
return t;
}
/** Get the front element. */
int peek() { //同上,但不用删除栈1的栈顶元素
while (s1.size() > 1) s2.push(s1.top()), s1.pop();
int t = s1.top();
while (s2.size()) s1.push(s2.top()), s2.pop();
return t;
}
/** Returns whether the queue is empty. */
bool empty() {
return s1.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();
*/