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) { int i = 0, j = 0; while (haystack[i] && needle[j]) { if(haystack[i] == needle[j]) { ++i; ++j; } else { i = i - j + 1; j = 0; } } return needle[j] ? 0 : haystack + i - j; } };