15. Find the Index of the First Occurrence in a String
Given strings haystack and needle, return the index of the first occurrence of needle in haystack, or -1 if it is not present.
Contoh 1:
Input: haystack = "sadbutsad", needle = "sad" Output: 0
Contoh 2:
Input: haystack = "leetcode", needle = "leeto" Output: -1
Batasan:
1 <= haystack.length, needle.length <= 10^4