Edit Distance

Given two words word1 and word2, find the minimum number of operations required to convert word1 to word2.

You have the following 3 operations permitted on a word:

1. Insert a character
2. Delete a character
3. Replace a character

Example 1:

Example 2:

java

class Solution {
    public int minDistance(String word1, String word2) {
        if (word1 == null || word2 == null) {
            return 0;
        }
        int[][] f = new int[word1.length() + 1][word2.length() + 1];
        for (int i = 0; i < word1.length() + 1; i++) {
            f[i][0] = i;
        }
        for (int i = 0; i < word2.length() + 1; i++) {
            f[0][i] = i;
        }
        for (int i = 1; i < word1.length() + 1; i++) {
            for (int j = 1; j < word2.length() + 1; j++) {
                if (word1.charAt(i - 1) == word2.charAt(j - 1)) {
                    f[i][j] = f[i - 1][j - 1];
                } else {
                    f[i][j] = 1 + Math.min(f[i - 1][j - 1], Math.min(f[i - 1][j], f[i][j - 1]));
                }
            }
        }
        return f[word1.length()][word2.length()];
    }
}