题目链接: https://ac.nowcoder.com/acm/contest/882/F
因为看到数据也小,所以当时比赛的时候我们也尝试了爆搜,但是,T了,主要在于搜完了才去统计…
代码
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MAXN = 35;
int n;
long long ans;
long long mp[MAXN][MAXN];
long long a[MAXN], b[MAXN];
void dfs(int now, ll sum, int suma, int sumb){
if(now > (2 * n) + 1){return ;}
if(suma == n && sumb == n){
ans = max(ans, sum);
return ;
}
if(suma < n){
a[suma + 1] = now;
for(int j = 1; j <= sumb; j++){
sum += mp[now][b[j]];
}
dfs(now + 1, sum, suma + 1, sumb);
for(int j = 1; j <= sumb; j++){
sum -= mp[now][b[j]];
}
}
if(sumb < n){
b[sumb + 1] = now;
for(int j = 1; j <= suma; j++){
sum += mp[now][a[j]];
}
dfs(now + 1, sum, suma, sumb + 1);
for(int j = 1; j <= suma; j++){
sum -= mp[now][a[j]];
}
}
return ;
}
int main()
{
ios::sync_with_stdio(false);
while(cin >> n){
for(int i = 1; i <= 2 * n; i++){
for(int j = 1; j <= 2 * n; j++){
cin >> mp[i][j];
}
}
ans = -1;
dfs(1, 0, 0, 0);
cout << ans << endl;
}
return 0;
}