Implement strstr()

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:

Input: haystack = "hello", needle = "ll"
Output: 2

答案

class Solution {
    public int strStr(String haystack, String needle) {
        if(needle.equals("")) return 0;
        for(int i = 0; i < haystack.length(); i++) {
            char h = haystack.charAt(i);
            int j = 0;
            if(i + needle.length() <= haystack.length() && h == needle.charAt(0)) {
                for(j = 0; j < needle.length(); j++) {
                    if(needle.charAt(j) != haystack.charAt(i + j))
                        break;
                }
                if(j == needle.length()) return i;
            }
        }
        return -1;
    }
}