Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.
Input: (haystack = 'hello'), (needle = 'll')
Output: 2
Input: (haystack = 'aaaaa'), (needle = 'bba')
Output: -1Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.
Input: (haystack = 'hello'), (needle = 'll')
Output: 2
Input: (haystack = 'aaaaa'), (needle = 'bba')
Output: -1