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algo/java/09_queue/DynamicArrayQueue.java at master · open-source-backup/algo · GitHub

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package queue;

/**

* Created by wangzheng on 2018/10/9.

*/

public class DynamicArrayQueue {

// 数组：items，数组大小：n

private String[] items;

private int n = 0;

// head表示队头下标，tail表示队尾下标

private int head = 0;

private int tail = 0;

// 申请一个大小为capacity的数组

public DynamicArrayQueue(int capacity) {

items = new String[capacity];

n = capacity;

}

// 入队操作，将item放入队尾

public boolean enqueue(String item) {

// tail == n表示队列末尾没有空间了

if (tail == n) {

// tail ==n && head==0，表示整个队列都占满了

if (head == 0) return false;

// 数据搬移

for (int i = head; i < tail; ++i) {

items[i-head] = items[i];

}

// 搬移完之后重新更新head和tail

tail -= head;

head = 0;

}

items[tail] = item;

tail++;

return true;

}

// 出队

public String dequeue() {

// 如果head == tail 表示队列为空

if (head == tail) return null;

// 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

String ret = items[head];

++head;

return ret;

}

public void printAll() {

for (int i = head; i < tail; ++i) {

System.out.print(items[i] + " ");

}

System.out.println();

}

}

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