712. 两个字符串的最小ASCII删除和 
思路 
看完题感觉跟前两天的题目1458高度相似，解法也差不多，还是dp。 
状态转移方程dp[i][j] = min(dp[i - 1][j] + s1[i - 1], dp[i][j - 1] + s2[j - 1], dp[i - 1][j - 1] + (s1[i - 1] == s2[j - 1] ? 0 : s1[i - 1] + s2[j - 1])) 
代码 
class Solution {
    public int minimumDeleteSum(String s1, String s2) {
        byte[] c1 = s1.getBytes();
        byte[] c2 = s2.getBytes();
        int m = c1.length, n = c2.length;
  ...