EditDistance.java

package dynamic_programming;

/**
 * Description: https://leetcode.com/problems/edit-distance
 * Difficulty: Hard
 * Time complexity: O(m * n)
 * Space complexity: O(m * n)
 */
public class EditDistance {

    public int minDistance(String word1, String word2) {
        int[][] dp = new int[word1.length() + 1][word2.length() + 1];
        for (int i = 0; i <= word1.length(); i++) dp[i][0] = i;
        for (int j = 0; j <= word2.length(); j++) dp[0][j] = j;

        for (int i = 1; i <= word1.length(); i++) {
            for (int j = 1; j <= word2.length(); j++) {
                if (word1.charAt(i - 1) == word2.charAt(j - 1)) {
                    dp[i][j] = dp[i - 1][j - 1];
                } else {
                    int replace = dp[i - 1][j - 1];
                    int insert = dp[i][j - 1];
                    int delete = dp[i - 1][j];

                    dp[i][j] = Math.min(replace, Math.min(insert, delete)) + 1;
                }
            }
        }

        return dp[word1.length()][word2.length()];
    }
}