luogu p4141 消失之物

洛谷p4141 前后两遍法
同Eden的新背包

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

using namespace std;
int n, m;
#define N 2010
#define M 2010
int v[N];
int f[N][M];
int g[N][M];

int Count(int i, int x) {
    int val = 0;
    for (int y = 0; y <= x; y++) {
        val += ((f[i - 1][y]%10)* (g[i + 1][x - y])%10);
        val%=10;
    }

    return val % 10;
}

int main() {
    cin >> n >> m;
    for (int i = 1; i <= n; i++) {
        cin >> v[i];
    }

    g[n+1][0] = 1;
    f[0][0] = 1;



    for (int i = 1; i <= n; i++) {
        for (int j = 0; j <= m; j++) {
            f[i][j] = f[i-1][j];
            if(j>=v[i])
                f[i][j] += f[i - 1][j - v[i]];
                f[i][j] %= 10;
        }
    }

    for(int i = n;i;i--){
        for(int j = 0;j<=m;j++){
            g[i][j] = g[i+1][j];
            if(j>=v[i])
                g[i][j] += g[i+1][j-v[i]];
                g[i][j] %= 10;
        }
    }

    for(int i = 1;i<=n;i++){
        for(int j=1;j<=m;j++){
            cout<<Count(i,j);
        }
        cout<<endl;
    }

    return 0;


}```