Given two strings needle and haystack, return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack. Clarification: What should we return when needle is an ...

//Runtime: 4 ms, faster than 63.59% of Java online submissions for Implement strStr(). //Memory Usage: 38.6 MB, less than 29.59% of Java online submissions for Implement strStr().