28. Implement strStr()

 1 class Solution {
 2     public int strStr(String haystack, String needle) {
 3         if(needle == null) return 0;
 4         if(haystack.length() < needle.length()) return -1;
 5         int nlen = needle.length();
 6         int res = -1;
 7         for(int i = 0; i < haystack.length() - nlen + 1; i++) {
 8             if(needle.equals(haystack.substring(i, i+nlen))) {
 9                 return i;
10             }
11         }
12         return res;
13         
14     }
15 }