Leetcode 28 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

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().

1)

class Solution { public int strStr(String haystack, String needle) { if(haystack.length() == 0 && needle.length() == 0){ return 0; }else if(haystack == null || haystack.length() == 0){ return -1; } int index = haystack.indexOf(needle); if(index > -1){ return index; }else{ return -1; } } }

2)

class Solution { public int strStr(String haystack, String needle) { return (needle.isEmpty() || haystack.indexOf(needle) == 0) ? 0 : haystack.indexOf(needle); } }

可以直接使用库函数或者是自己手动的进行匹配。