[LeetCode] Implement strStr()

Implement strStr().

Returns a pointer to the first occurrence of needle in haystack, or null if needle is not part of haystack.

class Solution {
public:
char *strStr(char *haystack, char *needle) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
int hayLen = strlen(haystack);
int needLen = strlen(needle);

for(int i = 0; i <= hayLen - needLen; i++)
{
char *p = haystack + i;
char *q = needle;
while(*q != '\0')
{
if (*p != *q)
break;
else
{
p++;
q++;
}
}

if (*q == '\0')
return haystack + i;
}

return NULL;
}
};