Given two words word1 and word2, find the minimum number of steps required to convert word1 to word2. (each operation is counted as 1 step.)You have the following 3 operations permitted on a word:a) Insert a characterb) Delete a characterc) Replace a character

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