POJ-2421 D - Constructing Roads

Constructing Roads
Time Limit: 2000MS   Memory Limit: 65536K
Total Submissions: 22053   Accepted: 9392

Description

There are N villages, which are numbered from 1 to N, and you should build some roads such that every two villages can connect to each other. We say two village A and B are connected, if and only if there is a road between A and B, or there exists a village C such that there is a road between A and C, and C and B are connected. 

We know that there are already some roads between some villages and your job is the build some roads such that all the villages are connect and the length of all the roads built is minimum.

Input

The first line is an integer N (3 <= N <= 100), which is the number of villages. Then come N lines, the i-th of which contains N integers, and the j-th of these N integers is the distance (the distance should be an integer within [1, 1000]) between village i and village j. 

Then there is an integer Q (0 <= Q <= N * (N + 1) / 2). Then come Q lines, each line contains two integers a and b (1 <= a < b <= N), which means the road between village a and village b has been built.

Output

You should output a line contains an integer, which is the length of all the roads to be built such that all the villages are connected, and this value is minimum.

Sample Input

3
0 990 692
990 0 179
692 179 0
1
1 2

Sample Output

179

Source

PKU Monthly,kicc

问题简单描述:

给定村庄,实现村庄之间接通的最小花费,唯一难点在于有些村庄之间已实现连通,

难点:怎么处理已连通村庄。

解决方法:将已连通村庄的公路花费记为0.

#include
#include
#include
int path[1005][1005],road[1005],flag[1005]={0};
int  main()
{
	memset(road,0,sizeof(road));
	memset(path,1,sizeof(path));
	int n,m,i,j;
	scanf("%d",&n);
	for(i=1;i<=n;i++)
	{
		for(j=1;j<=n;j++)
		{
			scanf("%d",&m);
			path[i][j]=m;
		}
	}
	int x,y,z,sum=0;
	scanf("%d",&x);
	for(i=1;i<=x;i++)
	{
		scanf("%d%d",&y,&z);
		path[y][z]=path[z][y]=0;//将已连通的村庄路费归为0
	}
	for(i=1;i<=n;i++)
		road[i]=path[1][i];
	for(i=2;i<=n;i++)
	{

		int r=1005,c;
		for(j=2;j<=n;j++)
		{
			if(flag[j]==0 && road[j]




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