题解 | #牛群编号变更#

import java.util.*;


public class Solution {
    /**
    常规dfs和动态规划，各位看官可自行选择
     */
    public static int minDistance (String word1, String word2) {
        int len1 = word1.length();
        int len2 = word2.length();
        int[][] dp = new int[len1 + 1][len2 + 1];
        dp[0][0] = 0;
        for (int i = 1; i <= len1; i++) {
            dp[i][0] = i;
        }
        for (int i = 1; i <= len2; i++) {
            dp[0][i] = i;
        }
        for (int i = 1; i <= len1; i++) {
            for (int j = 1; j <= len2; j++) {
                if (word1.charAt(i - 1) == word2.charAt(j - 1)) {
                    dp[i][j] = dp[i - 1][j - 1];
                } else {
                    dp[i][j] = 1 + Math.min(dp[i][j - 1], dp[i - 1][j]);
                }
            }
        }
        return dp[len1][len2];
    }
    StringBuilder s1 = new StringBuilder();
    StringBuilder s2 = new StringBuilder();
    public int minDistance2 (String word1, String word2) {
        s1.append(word1);
        s2.append(word2);
        return dfs(s1, s2);
    }
    public int dfs(StringBuilder s1, StringBuilder s2) {
        if (s1.length() != 0 && s2.length() == 0 || s1.length() == 0 &&
                s2.length() != 0) {
            return s1.length() == 0 ? s2.length() : s1.length();
        }
        if (s1.length() == 0 && s2.length() == 0) {
            return 0;
        }
        if (s1.charAt(0) == s2.charAt(0)) {
            return dfs(s1.deleteCharAt(0), s2.deleteCharAt(0));
        } else {
            return 1 + dfs(s1.deleteCharAt(0), s2);
        }
    }
}