POJ 2421 Controucting Roads Kruskyal+そして集を調べます。

http://poj.org/problem?id=2421
無向図の最小生成ツリーKruskyalアルゴリズム
Constructing Roads
Time Limit: 2000 MS
 
メモリLimit: 65536 K
Description
The e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e nected. 
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 builit minimum.
Input
The first line is an integer N(3==N==100)、which is the number of villages.The n come N lines、the i-th of which contains N integers、and the j-th of these N integers is the divistance(the distance) 
The n there is an integer Q(0<=N*(N+1)/2).The n come Q lines，each line contains two integers a and b(1<=a<=N），which means the road between village a and village a.hallage.
Output
You shoutput 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

/* Author : yan
 * Question : POJ 2421 Constructing Roads
 * Date && Time : Saturday, January 29 2011 05:27 PM
 * Compiler : gcc (Ubuntu 4.4.3-4ubuntu5) 4.4.3
*/
#include<stdio.h>
#define MAX 101
int map[MAX][MAX];
int father[MAX];
int rank[MAX];
typedef struct _route
{
	int x,y;
	int weight;
}Route;
Route route[MAX*MAX/2];
int route_cnt;
int ans;

void initial()
{
	unsigned i;
	for(i=0;i<MAX;i++) father[i]=i;
}
int Find_Set(int x)
{
	if(x!=father[x]) father[x]=Find_Set(father[x]);
	return father[x];
}
int Union_Set(int x,int y,int w)
{
	int a=Find_Set(x);
	int b=Find_Set(y);
	if(a==b) return 0;
	if(rank[x]<rank[y])
	{
		father[a]=b;
	}
	else
	{
		father[b]=a;
		if(rank[x]==rank[y]) rank[x]++;
	}
	ans+=w;
	return 1;
}
int cmp(const void *a,const void *b)
{
	return (*(Route *)a).weight - (*(Route *)b).weight;
}
int main()
{
	//freopen("input","r",stdin);
	unsigned n,i,j;
	initial();
	scanf("%d",&n);
	for(i=0;i<n;i++)
	{
		for(j=0;j<n;j++) scanf("%d",&map[i][j]);
	}
	unsigned q;
	scanf("%d",&q);
	unsigned x,y;
	for(i=0;i<q;i++)
	{
		scanf("%d %d",&x,&y);
		x--,y--;
		map[x][y]=0;
		map[y][x]=0;
	}
	for(i=0;i<n;i++)
	{
		for(j=i+1;j<n;j++)
		{
			route[route_cnt].x=i;
			route[route_cnt].y=j;
			route[route_cnt].weight=map[i][j];
			route_cnt++;
		}
	}
	qsort(route,route_cnt,sizeof(route[0]),cmp);

	for(i=0;i<route_cnt;i++)
	{
		Union_Set(route[i].x,route[i].y,route[i].weight);
		//printf("%d %d %d/n",route[i].x,route[i].y,route[i].weight);
	}
	printf("%d",ans);
	return 0;
}