28. Implement strStr()

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本文介绍了一个简单的Python实现strStr()函数的方法。该函数用于返回子串在主串中首次出现的位置索引，若子串不存在则返回-1。特别地，当子串为空字符串时，按照C和Java的标准返回0。

28. Implement strStr()
- 题目
- 代码：

28. Implement strStr()

easy

题目

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().

代码：

class Solution:
    def strStr(self, haystack, needle):
        """
        :type haystack: str
        :type needle: str
        :rtype: int
        """
        if needle=="":
            return 0
        if needle in haystack:
            return haystack.index(needle)
        else:
            return -1