LeetCode28 子字符串的位置

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().

public int strStr(String haystack, String needle) {
        if(needle.length() > haystack.length()){
            return -1;
        }
        for(int i = 0; ; i++){
            for(int j = 0; j <= needle.length(); j++){
                if(j == needle.length()) return i;
                if(i + j == haystack.length()) return -1;
                if(needle.charAt(j) != haystack.charAt(i + j)) break;
            }
        }
    }