Java数据结构 队列的实现(循环队列) 以及习题练习

队列

循环队列的实现

package Queue;

public interface Queue_i <T>{

    /**
     * 出队
     */
    T deQueue();
    /**
     * 入队
     */
    void enQueue(T val);

    /**
     * 获取队头元素
     */
    T getHead();

    /**
     * 获取队列长度
     */
    int getLength();
    /**
     * 是否为空队列
     */
    boolean isEmpty();


}

package Queue;

public class QueueImplement<T> implements Queue_i<T> {
    //队头指针
    private int front = 0;
    //队尾指针
    private int rear = 0;
    //队列容量
    private int maxSize = 0;

    //队列元素个数
    private int size = 0;
    //循环队列的数组
    private T[] loopArr;

    public QueueImplement() {
        this.loopArr = (T[]) new Object[10];
        this.maxSize = 10;

    }

    public QueueImplement(int maxSize) {
        this.loopArr = (T[]) new Object[maxSize];
        this.maxSize = maxSize;
    }

    @Override
    public T deQueue() {
        if (this.isEmpty()) {
            throw new RuntimeException("空队列");
        }
        T val = this.loopArr[front];
        this.front = (this.front+1)%this.maxSize;
        this.size--;

        //检查是否需要缩容
        if(this.size<(this.maxSize+1)/4&&this.maxSize>4) {
            this.resetSize((this.maxSize+1) / 4);
        }
        return val;
    }

    @Override
    public void enQueue(T val) {
        if ((this.rear + 1) % this.maxSize == this.front) {
            this.resetSize(this.maxSize * 2);
        }
        this.loopArr[this.rear] = val;
        this.rear = (this.rear+1)% this.maxSize;
        this.size++;
    }

    @Override
    public T getHead() {
        if (this.isEmpty()) {
            throw new RuntimeException("空队列");
        }
        return this.loopArr[this.front];
    }

    @Override
    public int getLength() {
        if (this.isEmpty()) {
            return 0;
        }
        return this.size;
    }

    @Override
    public boolean isEmpty() {
        return this.front == this.rear;
    }

    public int getMaxSize() {
        return maxSize;
    }

    //修改数组容量
    public void resetSize(int newMaxSize) {
        T[] newLoopArr = (T[]) new Object[newMaxSize];
        for (int i = 0; i < this.size; ++i) {
            newLoopArr[i] = loopArr[(this.front + i) % maxSize];
        }
        this.front = 0;
        this.rear = this.size;
        this.loopArr = newLoopArr;
        this.maxSize = newMaxSize;
    }
}

自己写一个简单的测试文件

单调队列

225. 用队列实现栈