两个栈实现队列
题目很简单,今天看了下Java泛型的东西,用泛型改写了一下:
package com.wy.oj; import java.util.Stack; /** * Created by wy on 2016/12/23 023. */ public class TwoStackQueue<T> { private Stack<T> s1 = new Stack<>(); // 入队 private Stack<T> s2 = new Stack<>(); // 出队 public T pop() { if (isEmpty()) return null; if (!s2.isEmpty()) return s2.pop(); else { while (!s1.isEmpty()) s2.push(s1.pop()); return s2.pop(); } } public void push(T item) { s1.push(item); } public int size() { return s1.size() + s2.size(); } public boolean isEmpty() { return (s1.isEmpty() && s2.isEmpty()); } // 测试 public static void main(String[] args) { TwoStackQueue<String> qs = new TwoStackQueue<>(); for (String s : "qing li si nian chun".split(" ")) qs.push(s); for (int i=0; i<3; ++i) System.out.println(qs.pop()); System.out.println(); for (String s : "ten zi jing".split(" ")) qs.push(s); while (!qs.isEmpty()) System.out.println(qs.pop()); TwoStackQueue<Integer> qi = new TwoStackQueue<>(); for (int i=10; i<100; i=2*i) qi.push(i); while (!qi.isEmpty()) System.out.println(qi.pop()); } }