NOIP2000 乘积最大

#include<iostream>
#include<cstdio>
#include<string>
#include<cstring>
#include<algorithm>

using namespace std;
const int maxn = 300;
int n,m,u,j;
long long int num,sum[maxn][maxn],dp[maxn][maxn];
int main(){
    memset(dp,0,sizeof(dp));
    cin>>n>>m>>num;
    for(int i = 1;i <= n;i++){
        sum[i][i] = num % 10;
        num /= 10;
    }
    u = 10;
    for(int l = 2;l <= n;l++){ 
        for(int i = 1;i <= n - l + 1;i++){
            j = i + l - 1;
            sum[i][j] = sum[i][j-1] + u * sum[j][j];
        }
        u *= 10;
    }
    for(int i = 1;i <= n;i++) dp[0][i] = sum[1][i];
    for(int i = 1;i <= m;i++){
        for(int j = i+1;j <= n;j++){
            for(int k = i;k < j;k++){
                dp[i][j] = max(dp[i][j],dp[i-1][k] * sum[k+1][j]);
            }
        }
    }
    cout<<dp[m][n];
    return 0;
}