LeetCode---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

从字符串中返回给定子串的开始的索引

可以直接使用python的find()方法一次完成

class Solution: def strStr(self, haystack, needle): return haystack.find(needle)

也可以从字符串开始的位置，依次比较和子字符串相同长度的串，看是否相同

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