Edit Distance

72. Edit Distance

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 character
b) Delete a character
c) Replace a character

public class Solution {  
    public int minDistance(String word1, String word2) {
        if (word1 == null || word2 == null) {
            return 0;
        }

        int m = word1.length(), n = word2.length();

        int[][] dp = new int[m + 1][n + 1];
        dp[0][0] = 0;

        for (int i = 0; i <= m; i++) {
            dp[i][0] = i;
        }

        for (int j = 0; j <= n; j++) {
            dp[0][j] = j;
        }

        for (int i = 1; i <= m; i++) {
            for (int j = 1; j <= n; j++) {
                if (word1.charAt(i - 1) == word2.charAt(j - 1)) {
                    dp[i][j] = dp[i - 1][j - 1];
                } else {
                    int min = Math.min(dp[i - 1][j - 1], Math.min(dp[i - 1][j], dp[i][j - 1]));
                    dp[i][j] = min + 1;
                }
            }
        }

        return dp[m][n];
    }
}

Hope this helps,
Michael