More than 19 cattle off summer school round2 F dfs

Topic Portal // res tp nowcoder

dfs

First all attributed to a team, after removing a person from the team placed in another team.

#include<iostream>
#include<cstdio>
#include<vector>
using namespace std;
typedef long long ll;
int n;
const int L = 30;
ll a[L][L];
ll sum[L];
ll ans;
vector<int>v;
void dfs(int x,ll re){
    int len = v.size();
    if(len == n){ans = ans>re?ans:re;return;}//队满
    if(x>2*n) return;//越界
    if(x >n + 1 + len) return;//即使将剩下的人全部划分到另一队，其人数也不足n
    ll t = sum[x];
    for(auto s:v) t -= a[x][s]*2;
    v.push_back(x);
    dfs(x+1,re + t);
    v.pop_back();
    dfs(x+1,re);
}
int main(){
    scanf(" %d",&n);
    for(int i = 1;i<=n*2;++i)
        for(int j = 1;j<=n*2;++j){
            scanf(" %lld",&a[i][j]);
            sum[i] += a[i][j];
        }
    dfs(1,0);
    printf("%lld\n",ans);
}