Implement strStr().

Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

 

分析：

给出两个字符串，查询第二个字符串是否在第一个字符串中出现过，如果有，就返回第一次出现的位置。

 

If source = "source" and target = "target", return -1.

If source = "abcdabcdefg" and target = "bcd", return 1.

 

public class Solution {    public int strStr(String haystack, String needle) {        if (haystack == null || needle == null){            return -1;        }                for (int i = 0; i < haystack.length() - needle.length() + 1; i++){            int j = 0;            for (j = 0; j < needle.length(); j++){                if (haystack.charAt(i + j) != needle.charAt(j)){                    break;                }            }            if (j == needle.length()){                return i;            }        }        return -1;    }}