package com.test;/*** Created by Demrystv.*/
public class isRotation {/*** 方法一：直接利用String的contains 方法* @param a* @param b* @return*//*如果a 和b 的长度一样长，先生成一个大字符串b2, b2=b+b，即b2就是两个b 拼接起来的，然后看b2 中是否包含a,如果包含a, 说明a 和b 互为旋转词， 如果不包含，说明不是互为旋转词。*/public boolean isRotation1(String a, String b){if (a == null || b == null || a.length() != b.length()){return false;}String b2 = b + b;return b2.contains(a);// 可以看其底层实现过程
    }/*** 方法二：看contains方法的源码，套用它的源码的方法* @param a* @param b* @return*/public boolean isRotation2(String a, String b){if (a == null || b == null || a.length() != b.length()){return false;}String b2 = b + b;return indexOf(b2, a, 0) > -1;}private int indexOf(String b2, String a, int index){char[] source = b2.toCharArray();char[] target = a.toCharArray();return func(source, 0, source.length, target, 0, target.length, index);}private int func(char[] source, int sourceOffset, int sourceCount,char[] target, int targetOffset, int targetCount,int fromIndex) {if (fromIndex >= sourceCount) {return (targetCount == 0 ? sourceCount : -1);}if (fromIndex < 0) {fromIndex = 0;}if (targetCount == 0) {return fromIndex;}char first = target[targetOffset];int max = sourceOffset + (sourceCount - targetCount);for (int i = sourceOffset + fromIndex; i <= max; i++) {if (source[i] != first) {while (++i <= max && source[i] != first);}if (i <= max) {int j = i + 1;int end = j + targetCount - 1;for (int k = targetOffset + 1; j < end && source[j]== target[k]; j++, k++);if (j == end) {return i - sourceOffset;}}}return -1;}

}