57 lines
1.3 KiB
Java
57 lines
1.3 KiB
Java
package queue;
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/**
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* Created by wangzheng on 2018/10/9.
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*/
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public class DynamicArrayQueue {
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// 数组：items，数组大小：n
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private String[] items;
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private int n = 0;
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// head表示队头下标，tail表示队尾下标
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private int head = 0;
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private int tail = 0;
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// 申请一个大小为capacity的数组
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public DynamicArrayQueue(int capacity) {
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items = new String[capacity];
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n = capacity;
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}
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// 入队操作，将item放入队尾
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public boolean enqueue(String item) {
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// tail == n表示队列末尾没有空间了
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if (tail == n) {
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// tail ==n && head==0，表示整个队列都占满了
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if (head == 0) return false;
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// 数据搬移
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for (int i = head; i < tail; ++i) {
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items[i-head] = items[i];
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}
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// 搬移完之后重新更新head和tail
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tail -= head;
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head = 0;
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}
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items[tail] = item;
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tail++;
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return true;
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}
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// 出队
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public String dequeue() {
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// 如果head == tail 表示队列为空
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if (head == tail) return null;
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// 为了让其他语言的同学看的更加明确，把--操作放到单独一行来写了
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String ret = items[head];
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++head;
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return ret;
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}
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public void printAll() {
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for (int i = head; i < tail; ++i) {
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System.out.print(items[i] + " ");
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}
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System.out.println();
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}
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}
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