AcWing 275. 传纸条

#include<iostream>
using namespace std ;
const int N=;
int f[*N][N][N];
int w[N][N];
int n,m;
int main() {
    cin>>n>>m;
    for(int i=; i<=n; i++)
        for(int j=; j<=m; j++)
            cin>>w[i][j];
    for(int k=; k<=m+n; k++)
        for(int i1=; i1<=n; i1++)
            for(int i2=; i2<=n; i2++) {
                int j1=k-i1,j2=k-i2;
                if(j1<||j2<||j1>m||j2>m)
                    continue;
                int s=w[i1][j1];
                if(i1!=i2) s+=w[i2][j2];
                f[k][i1][i2]=max(f[k][i1][i2],f[k-][i1-][i2]+s);
                f[k][i1][i2]=max(f[k][i1][i2],f[k-][i1][i2-]+s);
                f[k][i1][i2]=max(f[k][i1][i2],f[k-][i1-][i2-]+s);
                f[k][i1][i2]=max(f[k][i1][i2],f[k-][i1][i2]+s);
            }
    cout<<f[n+m][n][n]<<endl;
    return ;
}