[LeedCode OJ]#28 Implement strStr()

class Solution
{
public:
    int strStr(string haystack, string needle)
    {
        int len1 = haystack.length(),len2 = needle.length();
        int i,j;
        if(len2>len1) return -1;
        if(len1 == len2 && haystack!=needle) return -1;
        for(i = 0; i<=len1-len2; i++)
        {
            for(j = 0; j<len2; j++)
            {
                if(haystack[i+j]!=needle[j])
                    break;
            }
            if(j == len2)
                return i;
        }
        return -1;
    }
};