Floyd最小环Hdu1599

http://acm.hdu.edu.cn/showproblem.php?pid=1599

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <stack>
#include <queue>
#include <vector>
#include <map>
#include <string>
#include <iostream>
using namespace std;
const int INF=0xfffffff;
int Min(int a,int b)
{
	return a>b?b:a;
}
int Map[1111][1111];
int dp[1111][1111];
int main()
{
	int n,m;
	//freopen("in.txt","r",stdin);
	//freopen("out.txt","w",stdout);
	while(scanf("%d%d",&n,&m)!=EOF){
		int ans=INF;
		for(int i=1;i<=n;i++)
			for(int j=1;j<=n;j++)
			Map[i][j]=INF;
		for(int i=0;i<m;i++){
			int a,b,c;
			scanf("%d%d%d",&a,&b,&c);
			if(Map[a][b]>c){
				Map[a][b]=Map[b][a]=c;
			}
		}
		for(int i=1;i<=n;i++)
			for(int j=1;j<=n;j++)
			dp[i][j]=Map[i][j];
		for(int k=1;k<=n;k++){
			for(int i=1;i<=n;i++){
				for(int j=1;j<=n;j++)
					ans=Min(ans,dp[i][j]+Map[k][i]+Map[k][j]);
			}
			for(int i=1;i<=n;i++)
			for(int j=1;j<=n;j++){
				if(dp[i][j]>dp[i][k]+dp[k][j])
					dp[i][j]=dp[i][k]+dp[k][j];
			}
		}
		if(ans==INF)
			printf("It's impossible.\n");
		else
			printf("%d\n",ans);
	}
	return 0;
}