原题链接
Implement the following Operations of a stack using queues.
push(x) – Push element x onto stack. pop() – Removes the element on top of the stack. top() – Get the top element. empty() – Return whether the stack is empty. Notes: You must use only standard operations of a queue – which means only push to back, peek/pop from front, size, and is empty operations are valid. Depending on your language, queue may not be supported natively. You may simulate a queue by using a list or deque (double-ended queue), as long as you use only standard operations of a queue. You may assume that all operations are valid (for example, no pop or top operations will be called on an empty stack).
要让队首的元素到对尾去，因为stack是先进后出，没次入队之后将队首元素再入队。
class MyStack { queue<int>q;public: /** Initialize your data structure here. */ MyStack() { } /** Push element x onto stack. */ void push(int x) { q.push(x); for(int i=0;i<q.size()-1;++i) { q.push(q.front()); q.pop(); } } /** Removes the element on top of the stack and returns that element. */ int pop() { int v=q.front(); q.pop(); return v; } /** Get the top element. */ int top() { return q.front(); } /** Returns whether the stack is empty. */ bool empty() { return q.empty(); }};新闻热点
疑难解答
