AcWing 20. 用两个栈实现队列(含注释)
原题链接
简单
class MyQueue {
public:
/** Initialize your data structure here. */
stack<int> s1,s2; //定义两个栈
MyQueue() {
}
/** Push element x to the back of queue. */
void push(int x) {
s1.push(x);
}
/** Removes the element from in front of queue and returns that element. */
int pop() {
while(s1.size()>1){ //s1除了第一个放到s2里
int a=s1.top();
s2.push(a);
s1.pop();
}
int t=s1.top(); //t等于s1第一个
s1.pop(); //s1此时只剩下1个,并且删了
while(s2.size()>=1){ //从s2中取出放回s1
int a=s2.top();
s1.push(a);
s2.pop();
}
return t;
}
/** Get the front element. */
int peek() { //除了不删除s1的头一个元素,其他和上面一样
while(s1.size()>1){
int a=s1.top();
s2.push(a);
s1.pop();
}
int t=s1.top();
while(s2.size()>=1){
int a=s2.top();
s1.push(a);
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();
*/
不一般~ ~