package com.zhongan;

import java.util.Scanner;

/**

* @author chenliyang

* @description 实现strStr()函数

* @date 2018/11/24

*/

public class Leetcode28 {

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

String haystack = sc.next();

String needle = sc.next();

System.out.println(strStr(haystack, needle));

}

private static int strStr(String haystack, String needle) {

if (needle.length() == 0) {

//如果needle为空字符串则返回0

return 0;

}

char[] haystackCharArray = haystack.toCharArray();

char[] needleCharArray = needle.toCharArray();

for (int i = 0; i < haystackCharArray.length; i++) {

//遍历haystack,找到needle中的第一个字符在haystack中出现的位置的下标

if (haystackCharArray[i] == needleCharArray[0]) {

//比较needle中其他的字符是否与haystack对应位置匹配

int index = i + 1;

int j;

for (j = 1; index < haystackCharArray.length && j < needleCharArray.length; j++) {

if (haystackCharArray[index] == needleCharArray[j]) {

//字符串中字符匹配则比较下一个字符

index++;

} else {

break;

}

}

if (j == needleCharArray.length) {

//字符串全部匹配则返回needle字符串第一个字符在haystack中出现位置的下标

return i;

}

}

}

//未匹配则返回-1

return -1;

}

}