hdu2122 Ice_cream’s world III(MST)

Ice_cream’s world III

Time Limit: 3000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)

Total Submission(s): 1250 Accepted Submission(s): 413



Problem Description

ice_cream’s world becomes stronger and stronger; every road is built as undirected. The queen enjoys traveling around her world; the queen’s requirement is like II problem, beautifies the roads, by which there are some ways from every city to the capital. The
project’s cost should be as less as better.



Input

Every case have two integers N and M (N<=1000, M<=10000) meaning N cities and M roads, the cities numbered 0…N-1, following N lines, each line contain three integers S, T and C, meaning S connected with T have a road will cost C.



Output

If Wiskey can’t satisfy the queen’s requirement, you must be output “impossible”, otherwise, print the minimum cost in this project. After every case print one blank.



Sample Input

2 1
0 1 10

4 0

Sample Output

10

impossible

Author

Wiskey



Source

HDU 2007-10 Programming Contest_WarmUp



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最小生成树 kruskal算法

#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;
struct node
{
	int a,b,cost;
}c[10005];
int fa[1005];
void init(int n)
{
	for(int i=0;i<n;i++)
	fa[i]=i;
}
bool cmp(node x,node y)
{
	return x.cost<y.cost;
}
int find(int x)
{
	if(fa[x]!=x) fa[x]=find(fa[x]);
	return fa[x];
}
int main()
{
	int n,k;
	while(~scanf("%d %d",&n,&k))
	{
		init(n);
		for(int i=0;i<k;i++)
		scanf("%d %d %d",&c[i].a,&c[i].b,&c[i].cost);
		sort(c,c+k,cmp);
		int sum=0;
		for(int i=0;i<k;i++)
		{
			int x=find(c[i].a);
			int y=find(c[i].b);
			if(x!=y)
			sum+=c[i].cost,fa[x]=y;
		}
		int count=0;
		for(int i=0;i<n;i++)
		if(fa[i]==i)
		count++;
		if(count!=1)
		printf("impossible\n\n");
		else
		printf("%d\n\n",sum);
	}
	return 0;
}