028ImplementStrStr().py

"""
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().
"""
"""
Comments
"""
"""
My
"""
class Solution(object):
    def strStr(self, haystack, needle):
        """
        :type haystack: str
        :type needle: str
        :rtype: int
        """
        
        if needle == '':
            return 0
        if len(haystack) == len(needle):
            if haystack == needle:
                return 0
        
        haystack = list(haystack)
        needle = list(needle)
        if len(haystack) < len(needle):
            return -1
        
        for i in range(len(haystack)-len(needle)+1):
            if haystack[i] == needle[0]:
                if haystack[i:i+len(needle)] == needle:
                    return i
        return -1
                
"""
Fast
"""
class Solution(object):
    def strStr(self, haystack, needle):
        """
        :type haystack: str
        :type needle: str
        :rtype: int
        """
        if needle == "":
            return 0
        for i in range(len(haystack) - len(needle)+1):
            if haystack[i:i+len(needle)] == needle:
                return i
        return -1