README.md

28. Implement strStr()

Implement strStr().

Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

Example 1:

Input: haystack = "hello", needle = "ll" Output: 2 

Example 2:

Input: haystack = "aaaaa", needle = "bba" Output: -1 

Clarification:

What should we return when needle is an empty string? This is a great question to ask during an interview.

For the purpose of this problem, we will return 0 when needle is an empty string. This is consistent to C's strstr() and Java's indexOf().

Solutions (Python)

1. Linear Scan

classSolution: defstrStr(self, haystack: str, needle: str) ->int: ifnotneedle: return0foriinrange(len(haystack) -len(needle) +1): flag=Trueforjinrange(0, len(needle)): ifhaystack[i+j] !=needle[j]: flag=Falsebreakifflag: returnireturn-1