HDU - 1599 find the mincost route(Floyd求最小环)

#include <cstdio>
#include <iostream>
#include <cstring>
#include <cmath>
#include <string>
#include <algorithm>
#include <queue>
#include <stack>
using namespace std;

#define ll long long
const ll INF = 1<<30;
const double PI = acos(-1.0);
const double e = 2.718281828459;
const double eps = 1e-8;
int n, m;
const int MAXN = 110;
ll g[MAXN][MAXN];
ll dist[MAXN][MAXN];

int Floyd()
{
    ll mincircle = INF;
    for(int k = 1; k <= n; k++)
    {   //<span><span class="comment">求最小环权值</span></span>
        for(int i = 1; i <= n; i++)
        {
            for(int j = 1; j <= n; j++)
            {
                if(i!=j && i!=k && j!=k && mincircle>dist[i][j]+g[i][k]+g[k][j])
                    mincircle = dist[i][j]+g[i][k]+g[k][j];
            }
        }
        for(int i = 1; i <= n; i++)
        {
            for(int j = 1; j <= n; j++)
            {
                if(dist[i][j] > dist[i][k]+dist[k][j])
                    dist[i][j] = dist[i][k]+dist[k][j];
            }
        }
    }
    return mincircle;
}

int main()
{
    //freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w", stdout);
    while(cin>>n>>m)
    {
        for(int i = 1; i <= n; i++)
        {
            for(int j = 1; j <= n; j++)
            {
                g[i][j] = (i==j)?0:INF;
            }
        }
        int p, q;
        ll w;
        for(int i = 1; i <= m; i++)
        {
            scanf("%d %d %lld", &p, &q, &w);
            if(g[p][q] > w)
                g[p][q] = g[q][p] = w;
        }
        for(int i = 1; i <= n; i++)
        {
            for(int j = 1; j <= n; j++)
            {
                dist[i][j] = g[i][j];
            }
        }
        cout<<INF<<endl;
        ll ans = Floyd();
        if(ans != INF)
            printf("%lld\n", ans);
        else
            printf("It's impossible.\n");
    }
    return 0;
}