idt 分配 最大 val work 解題思路 clu mit enter

題目代號：POJ 2531

題目鏈接：http://poj.org/problem?id=2531

Language: Default Network Saboteur

Time Limit: 2000MS		Memory Limit: 65536K
Total Submissions: 13290		Accepted: 6428

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

3
0 50 30
50 0 40
30 40 0

Sample Output

90

Source

Northeastern Europe 2002, Far-Eastern Subregion

題目大意：這個題就是題目有點難以理解，相當於有n臺服務器，現在要將n臺服務器分配成2個區域，不同區域之間的任意兩臺服務器會通過兩個區域之間的節點交換數據，現在要你求，節點通過的最大數據量是多少，第i行第j列的數值相當於第i臺服務器與第j臺服務器交換的數據量。

解題思路：dfs遍歷一遍，每遍歷一次獲取最大值，最後輸出就行了。

AC代碼：

# include <stdio.h>
# include <string
 
.h>
# include <stdlib.h>
# include <iostream>
# include <fstream>
# include <vector>
# include <queue>
# include <stack>
# include <map>
# include <math.h>
# include <algorithm>
using namespace std;
# define pi acos(-1.0)
# define mem(a,b) memset(a,b,sizeof(a))
# define FOR(i,a,n) for(int i=a; i<=n; ++i)
# define For(i,n,a) for(int i=n; i>=a; --i)
# define FO(i,a,n) for(int i=a; i<n; ++i)
# define Fo(i,n,a) for(int i=n; i>a ;--i)
typedef long long LL;
typedef unsigned long long ULL;

int a[25][25],ans,n;
int b[25];

void dfs(int num,int data)
{
    int s=data;
    b[num]=1;
    for(int i=1;i<=n;i++)
    {
        if(b[i])data-=a[num][i];
        else data+=a[num][i];
    }
    ans=max(ans,data);
    for(int i=num+1;i<=n;i++)
    {
        if(data>s)
        {
            dfs(i,data);
            b[i]=0;
        }
    }
    return;
}

int main()
{
    //freopen("in.txt", "r", stdin);
    while(~scanf("%d",&n))
    {
        for(int i=1;i<=n;i++)
            for(int j=1;j<=n;j++)
                scanf("%d",&a[i][j]);
        ans=0;
        mem(b,0);
        dfs(1,0);
        cout<<ans<<endl;
    }
    return 0;
}

POJ 2531 Network Saboteur（dfs）