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().

code

class Solution:
def strStr(self, haystack, needle):
"""
:type haystack: str
:type needle: str
:rtype: int
"""
j = -1
if haystack == "" and needle == "":
return 0
elif haystack != "" and needle == "":
return 0
elif haystack == "" and needle != "":
return -1
else:
for i in range(len(haystack) - len(needle) + 1):
if haystack[i:i+len(needle)] == needle:
j = i
break
return j

tips

1. j = -1
2. range 左闭右开
3. Python slice