[LeetCode] Implement strStr()

Implement strStr().

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

Update (2014-11-02):
The signature of the function had been updated to return the index instead of the pointer. If you still see your function signature returns a char * or String, please click the reload button  to reset your code definition.

思路：没用KMP，直接字符串比较，O（m*n）

class Solution {
    public:
        int strStr(char *haystack, char *needle) {

            int hayLen = strlen(haystack);
            int needLen= strlen(needle);

            for(int i = 0; i <= hayLen-needLen; i++)
            {
                int k = i;
                int j = 0;
                for(/* */; j <needLen; /* */)
                {
                    if(haystack[k] == needle[j])
                    {
                        k++;
                        j++;
                    }
                    else
                        break;
                }
                if(j == needLen)
                    return i;
            }
            return -1;

        }
};