Edit Distance

 1 public class Solution {
 2     /**
 3      * @param word1 & word2: Two string.
 4      * @return: The minimum number of steps.
 5      */
 6     public int minDistance(String word1, String word2) {
 7         // write your code here
 8         if(word1==null&&word2==null) {
 9             return 0;
10         }
11         else if(word1!=null&&(word2==null||word2.length()==0)){
12             return word1.length();
13         } else if ((word1==null||word1.length()==0)&&word2!=null){
14             return word2.length();  
15         }
16         
17         int len1 = word1.length();
18         int len2 = word2.length();
19         
20         int[][] t = new int[len1][len2];
21         
22         int i=0;
23         for(; i< len2;i++){
24             if(word1.charAt(0)==word2.charAt(i)){
25                 t[0][i] = i;
26                 break;
27             }else{
28                 t[0][i] = i+1;
29             }
30         }
31         for(;i<len2;i++){
32             t[0][i] = i;
33         }
34         i=0;
35         for(; i< len1;i++){
36             if(word2.charAt(0)==word1.charAt(i)){
37                 t[i][0] = i;
38                 break;
39             }else{
40                 t[i][0] = i+1;
41             }
42         }
43         for(;i<len1;i++){
44             t[i][0] = i;
45         }
46         
47         for(i=1; i< len1;i++){
48             for( int j=1;j<len2;j++){
49                 if(word1.charAt(i)==word2.charAt(j)){
50                     t[i][j] = Math.min(t[i-1][j-1], Math.min(t[i-1][j]+1, t[i][j-1]+1));
51                 }else{
52                     t[i][j] = Math.min(t[i-1][j-1], Math.min(t[i-1][j], t[i][j-1]))+1;
53                 }
54             }
55         }
56         return t[len1-1][len2-1];
57     }
58 }