使用栈实现队列的下列操作:
示例:
MyQueue queue = new MyQueue(); queue.push(1); queue.push(2); queue.peek(); // 返回 1 queue.pop(); // 返回 1 queue.empty(); // 返回 false
说明:
push to top
, peek/pop from top
, size
, 和 is empty
操作是合法的。class MyQueue { private Stack<Integer> stackPush; private Stack<Integer> stackPop; /** Initialize your data structure here. */ public MyQueue() { stackPush = new Stack<Integer>(); stackPop = new Stack<Integer>(); } /** Push element x to the back of queue. */ public void push(int x) { stackPush.push(x); } /** Removes the element from in front of queue and returns that element. */ public int pop() { if(stackPop.empty()){ while(!stackPush.empty()){ stackPop.push(stackPush.pop()); } } return stackPop.pop(); } /** Get the front element. */ public int peek() { if(stackPop.empty()){ while(!stackPush.empty()){ stackPop.push(stackPush.pop()); } } return stackPop.peek(); } /** Returns whether the queue is empty. */ public boolean empty() { return stackPush.empty() && stackPop.empty(); } } /** * 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(); * boolean param_4 = obj.empty(); */
原文:https://www.cnblogs.com/JAYPARK/p/10706990.html