class Solution:
    def strStr(self, haystack: str, needle: str) -> int:
        return haystack.find(needle)

def main():
    s = Solution()

    print(s.strStr("hello", "ll")) # 2
    print(s.strStr("aaaaa", "bba")) # -1

if __name__ == '__main__':
    main()
			

class Solution:
    def strStr(self, haystack: str, needle: str) -> int:
        if len(haystack) == 0 and len(needle) == 0:
            return 0

        if len(needle) == 0:
            return 0

        i = 0 # pointer for haystack
        j = 0 # pointer for needle

        while i < len(haystack):
            if haystack[i] == needle[j]:
                print(i, j, haystack[i], needle[j])
                i += 1
                j += 1
            else:
                print(i, j, haystack[i], needle[j])
                if j == 0:
                    i += 1
                else:
                    i -= j-1
                j = 0

            if j >= len(needle):
                break

        if j == len(needle):
            return i-len(needle)
        else:
            return -1

def main():
    s = Solution()

    print(s.strStr("hello", "ll")) # 2
    print(s.strStr("aaaaa", "bba")) # -1
    print(s.strStr("abcdcdeef", "cde")) # 4
    print(s.strStr("mississippi", "issip")) # 4
    print(s.strStr("mississippi", "issipi")) # -1
    print(s.strStr("a", "")) # 0

if __name__ == '__main__':
    main()