剑指offer

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package Chapter2;import java.util.Stack;/** * 面试题7：用两个栈实现队列 * 用两个栈来实现一个队列，完成队列的Push和Pop操作。 队列中的元素为int类型。 *//* * 思路： * 一个stack 用来 offer * 一个stack 用poll */public class _07_twoStack {public static void main(String[] args) {_07_function f = new _07_function();f.offer(4);f.offer(6);System.out.println(f.poll());f.offer(10);f.offer(14);System.out.println(f.poll());System.out.println(f.poll());f.offer(16);System.out.println(f.poll());System.out.println(f.poll());}}class _07_function {private Stack<Integer> offer_stack = new Stack<Integer>();private Stack<Integer> poll_stack = new Stack<Integer>();void offer(Integer value) {offer_stack.push(value);}Integer poll() {//if (poll_stack.isEmpty()) {//if(offer_stack.isEmpty()) {//return null;//} else {//while (!offer_stack.isEmpty()) {//poll_stack.push(offer_stack.pop());//}//return poll_stack.pop();//}//} else {//return poll_stack.pop();//}if (poll_stack.isEmpty() && offer_stack.isEmpty()) {return null;}if (poll_stack.isEmpty())while (!offer_stack.isEmpty()) poll_stack.push(offer_stack.pop());return poll_stack.pop();}}

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