class Solution {
public:
int minimumDeleteSum(string s1, string s2) {
int m = s1.size(),n = s2.size();
vector<vector<int>> dp(m+1,vector<int>(n+1,0));
for(int i=1;i<=n;i++)
dp[0][i] = dp[0][i-1]+ s2[i-1];
for(int i=1;i<=m;i++){
dp[i][0] = dp[i-1][0]+s1[i-1];
for(int j=1;j<=n;j++){
if(s1[i-1]==s2[j-1])dp[i][j]=dp[i-1][j-1];
else dp[i][j] = min(dp[i-1][j]+s1[i-1],dp[i][j-1]+s2[j-1]);
}
}
return dp[m][n];
}
};