Network Saboteur（dfs）

#include<stdio.h>
int n,ans = 0,map[21][21],set[21];
void dfs(int x, int sum)
{
    int i,m;
    if(x>n)
    {
        if(sum > ans)
            ans = sum;
        return;
    }
    m = 0;
    set[x] = 1;
    for(i = 1; i <= x; i ++)
        if(set[i] == 2)
            m += map[i][x];
    dfs(x + 1, sum + m);
    m = 0;
    set[x] = 2;
    for(i = 1; i <= x; i ++)
        if(set[i] == 1)
            m += map[i][x];
    dfs(x + 1, sum + m);
}
int main()
{
    int i,j;
    scanf("%d",&n);
    for(i = 1; i <= n; i ++)
        for(j = 1; j <= n; j ++)
            scanf("%d",&map[i][j]);
    dfs(1, 0);
    printf("%d\n",ans);
    return 0;
}