28. Implement strStr().py

class Solution:
    def strStr(self, haystack: str, needle: str) -> int:
        if len(needle) ==0:
            return 0
        needleL = len(needle)
        for i in range(0, len(haystack)):
            if haystack[i:i+needleL] == needle:
                return i
        return -1

      
      
      '''
      Implement strStr().

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 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().

 

Example 1:

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

Input: haystack = "aaaaa", needle = "bba"
Output: -1
Example 3:

Input: haystack = "", needle = ""
Output: 0
 

Constraints:

0 <= haystack.length, needle.length <= 5 * 104
haystack and needle consist of only lower-case English characters.
'''