poj 2531 Network Saboteur（DFS减枝）_a university network is composed of n computers. s-优快云博客

本文探讨了一种方法，通过重新组织大学网络中的计算机，旨在最大化两个子网络之间的流量。利用矩阵表示的交通数据，目标是将网络节点划分为两个互斥子集，从而计算并实现最大的跨子网络流量。

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题意：将n个计算机分成两部分，求权值的最大值

方法：先默认将所有的放入一个集合，然后将里面的元素一个一个的转移到另一个集合

Description

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

Output

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

Sample Input

Sample Output

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <cmath>
#include <algorithm>
#define RR freopen("in.txt","r",stdin)
#define WW freopne("out.txt","w",stdout)
#define LL long long
#define INF 0x3f3f3f3f
using namespace std;

int Map[50][50];
int dep[50];
int ans;
int n;

void DFS(int id,int data)
{
    dep[id] = 1;
    int tmp = data;
    for(int i=1;i<=n;i++)
    {
        if(dep[i] == 0)
            tmp += Map[i][id];
        else
            tmp -= Map[i][id];
    }
    if(ans < tmp)
        ans = tmp;
    for(int i=id+1;i<=n;i++)
    {
        if(tmp > data)
        {
            DFS(i,tmp);
            dep[i] = 0;
        }
    }

}
int main()
{
    while(cin>>n)
    {
        for(int i=1;i<=n;i++)
        {
            for(int j=1;j<=n;j++)
            {
                cin>>Map[i][j];
            }
        }
        ans = 0;
        memset(dep,0,sizeof(dep));
        DFS(1,0);
        printf("%d\n",ans);
    }
    return 0;
}