Longest Common Prefix

 1 public class Solution {
 2     
 3     // 1. Method 1, start from the first one, compare prefix with next string, until end;
 4     // 2. Method 2, start from the first char, compare it with all string, and then the second char
 5     // I am using method 1 here
 6     public String longestCommonPrefix(String[] strs) {
 7         if (strs == null || strs.length == 0) {
 8             return "";
 9         }
10         String prefix = strs[0];
11         for(int i = 1; i < strs.length; i++) {
12             int j = 0;
13             while( j < strs[i].length() && j < prefix.length() && strs[i].charAt(j) == prefix.charAt(j)) {
14                 j++;
15             }
16             if( j == 0) {
17                 return "";
18     }
19             prefix = prefix.substring(0, j);
20         }
21         return prefix;
22     }
23 
24 }