Implement strStr()

【问题描述】

Implement strStr().

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

【解决方案】

int strStr(char* haystack, char* needle) {
    if(NULL == needle)
    {
        return 0;
    }

    int i;
    int haystackLen = strlen(haystack);
    int needleLen = strlen(needle);

    if(haystackLen < needleLen)
    {
        return -1;
    }

    for(i=0; i<=(haystackLen - needleLen); i++)
    {
        if(0 == strncmp(haystack+i, needle, needleLen))
        {
            return i;
        }
    }

    return -1;
}