Network Saboteur(dfs)

Problem Description  点击打开链接

A university network is composed of N computers. System administrators gathered information on the traffic between nodes, and carefully divided the network into two subnetworks in order to minimize traffic between parts. 
A disgruntled computer science student Vasya, after being expelled from the university, decided to have his revenge. He hacked into the university network and decided to reassign computers to maximize the traffic between two subnetworks. 
Unfortunately, he found that calculating such worst subdivision is one of those problems he, being a student, failed to solve. So he asks you, a more successful CS student, to help him. 
The traffic data are given in the form of matrix C, where Cij is the amount of data sent between ith and jth nodes (Cij = Cji, Cii = 0). The goal is to divide the network nodes into the two disjointed subsets A and B so as to maximize the sum ∑Cij (i∈A,j∈B).

 

Input

The first line of input contains a number of nodes N (2 <= N <= 20). The following N lines, containing N space-separated integers each, represent the traffic matrix C (0 <= Cij <= 10000). <br>Output file must contain a single integer -- the maximum traffic between the subnetworks. <br>

 

Output

Output must contain a single integer -- the maximum traffic between the subnetworks.

 

Sample Input

  

   3
0 50 30
50 0 40
30 40 0

  

 

Sample Output

  

   90
  

//What fuck!!!!? 
//分成两组 求第一组的每一个点到第二个组的每一个点的距离的最大值是多少 
//刚开始都是在第二组，     没有被标记的一组 

#if 0                //Network Saboteur  
#include<iostream>
#include<cstring>
using namespace std;
bool vis[25];
int map[25][25],maxx,n;

void dfs(int x,int sum)
{
	int mx=sum;
	vis[x]=1;
	
	for(int j=0; j<n; j++)
	{
		if(vis[j]==0)
		{
			mx+=map[x][j];	
		}
		else
		{
			mx-=map[x][j];
		}
	
	}
		
	if(mx>maxx)
		maxx=mx;
	if(mx>sum)
	{
		for(int k=x+1; k<n; k++)
		{
			dfs(k,mx);
			vis[k]=0;
		}
			
	}	
	
}

int main()
{
	
	cin>>n;
	
	for(int i=0; i<n; i++)
	{
		for(int j=0; j<n; j++)
		{
			cin>>map[i][j];
		}
	}
	dfs(0,0);
	cout<<maxx<<endl;
	
}

#endif