Implement the following operations of a stack using queues.
Notes:
push to back
, peek/pop from front
, size
, and is empty
operations are valid.设计题,用队列实现栈。
太简单了,不用想太多。
class MyStack {
public:
queue<int> q;
/** Initialize your data structure here. */
MyStack() {}
/** Push element x onto stack. */
void push(int x) {
int n = q.size();
q.push(x);
while(n--)
{
q.push(q.front());
q.pop();
}
}
/** Removes the element on top of the stack and returns that element. */
int pop() {
int t = q.front();
q.pop();
return t;
}
/** Get the top element. */
int top() {
return q.front();
}
/** Returns whether the stack is empty. */
bool empty() {
return q.empty();
}
};
/**
* Your MyStack object will be instantiated and called as such:
* MyStack obj = new MyStack();
* obj.push(x);
* int param_2 = obj.pop();
* int param_3 = obj.top();
* bool param_4 = obj.empty();
*/