92 行
1.8 KiB
Java
92 行
1.8 KiB
Java
package com.mj.circle;
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@SuppressWarnings("unchecked")
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public class CircleQueue<E> {
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private int front;
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private int size;
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private E[] elements;
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private static final int DEFAULT_CAPACITY = 10;
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public CircleQueue() {
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elements = (E[]) new Object[DEFAULT_CAPACITY];
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}
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public int size() {
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return size;
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}
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public boolean isEmpty() {
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return size == 0;
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}
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public void clear() {
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for (int i = 0; i < size; i++) {
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elements[index(i)] = null;
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}
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front = 0;
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size = 0;
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}
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public void enQueue(E element) {
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ensureCapacity(size + 1);
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elements[index(size)] = element;
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size++;
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}
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public E deQueue() {
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E frontElement = elements[front];
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elements[front] = null;
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front = index(1);
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size--;
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return frontElement;
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}
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public E front() {
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return elements[front];
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}
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@Override
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public String toString() {
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StringBuilder string = new StringBuilder();
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string.append("capcacity=").append(elements.length)
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.append(" size=").append(size)
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.append(" front=").append(front)
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.append(", [");
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for (int i = 0; i < elements.length; i++) {
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if (i != 0) {
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string.append(", ");
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}
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string.append(elements[i]);
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}
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string.append("]");
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return string.toString();
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}
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private int index(int index) {
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index += front;
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return index - (index >= elements.length ? elements.length : 0);
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}
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/**
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* 保证要有capacity的容量
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* @param capacity
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*/
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private void ensureCapacity(int capacity) {
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int oldCapacity = elements.length;
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if (oldCapacity >= capacity) return;
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// 新容量为旧容量的1.5倍
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int newCapacity = oldCapacity + (oldCapacity >> 1);
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E[] newElements = (E[]) new Object[newCapacity];
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for (int i = 0; i < size; i++) {
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newElements[i] = elements[index(i)];
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}
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elements = newElements;
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// 重置front
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front = 0;
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}
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}
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