28. Implement strStr() ——Java

Implement strStr().

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

寻找haystack里面是否存在needle， 如果没有出现，返回-1.

特别注意：

1. needle不能比haystack长。

2. needle可以是""，此时return 0。

Run Code Result:×

Your input

"mississippi""issippi"

Your answer

4

Expected answer

4

class Solution {    public int strStr(String haystack, String needle) {        if(haystack.length() < needle.length())            return -1;        if(needle.length()==0)            return 0;        char[] hay = haystack.toCharArray();        char[] nee = needle.toCharArray();                for(int i=0; i<hay.length; i++){            int index = i;            for(int j=0; j<nee.length; j++){                 if(index==hay.length)                    return -1;                if(hay[index++] != nee[j])                    break;                if(j == nee.length-1)                    return i;            }        }        return -1;    }}