712. 两个字符串的最小ASCII删除和

解法一：动态规划

参考官方题解：https://leetcode-cn.com/problems/minimum-ascii-delete-sum-for-two-strings/solution/liang-ge-zi-fu-chuan-de-zui-xiao-asciishan-chu-he-/
想不到啊😟

class Solution {
    public int minimumDeleteSum(String s1, String s2) {
        final int len1 = s1.length();
        final int len2 = s2.length();
        // dp[i][j]表示s1[i:]和s2[j:]相等时的最小字符和
        int[][] dp = new int[len1 + 1][len2 + 1];
        dp[len1][len2] = 0;
        for (int i = len1 - 1; i >= 0; --i) {
            dp[i][len2] = dp[i + 1][len2] + s1.charAt(i);
        }
        for (int i = len2 - 1; i >= 0; --i) {
            dp[len1][i] = dp[len1][i + 1] + s2.charAt(i);
        }
        for (int i = len1 - 1; i >= 0; --i) {
            for (int j = len2 - 1; j >= 0; --j) {
                if (s1.charAt(i) == s2.charAt(j)) {
                    dp[i][j] = dp[i + 1][j + 1];
                } else {
                    dp[i][j] = Math.min(dp[i][j + 1] + s2.charAt(j), dp[i + 1][j] + s1.charAt(i));
                }
            }
        }
        return dp[0][0];
    }
}