Edit Distance

 1 public class Solution {
 2     public int minDistance(String word1, String word2) {
 3         int len1 = word1 == null ? 0 : word1.length();
 4         int len2 = word2 == null ? 0 : word2.length();
 5         if(len1 == 0) return len2;
 6         if(len2 == 0) return len1;
 7         int[][] map = new int[len1 + 1][len2 + 1];
 8         for(int i = 0; i <= len1; i ++)
 9             map[i][0] = i;
10         for(int i = 0; i <= len2; i ++)
11             map[0][i] = i;
12         for(int i = 1; i <= len1; i ++){
13             for(int j = 1; j <= len2; j ++){
14                 map[i][j] = Math.min(Math.min(map[i - 1][j], map[i][j - 1]) + 1, 
15                                      map[i - 1][j - 1] + (word1.charAt(i - 1) == word2.charAt(j - 1) ? 0 : 1));
16             }
17         }
18         return map[len1][len2];
19     }
20 }