LeetCode 28：Implement strStr()

Implement strStr().

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

实现函数strStr。代码如下：

int strStr(char* haystack, char* needle) {
    size_t len = strlen(haystack);
    if(strlen(needle) == 0)
    return 0;
    if(strcmp(haystack, needle) == 0)
        return 0;
    for(int i=0; i<len;i++){
        if(haystack[i] == needle[0]){
            if(strncmp(&(haystack[i]), needle, strlen(needle)) == 0)
                return i;
        }
    }
    return -1;

}