【LightOJ 1002】 Country Roads

【LightOJ 1002】 Country Roads

。。。又一个另类OJ。。。最长路 贴个SPFA的

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <queue>
#include <set>

using namespace std;

int mp[555][555];
int dis[555];
bool vis[555];
int n,m,tp,s;

void SPFA()
{
    memset(vis,0,sizeof(vis));
    memset(dis,-1,sizeof(dis));
    vis[s] = 1;
    queue <int> q;
    q.push(s);
    vis[s] = 1;
    dis[s] = 0;
    int u,v,w,i,k;
    while(!q.empty())
    {
        u = q.front();
        q.pop();
        vis[u] = 0;
        for(i = 0; i < n; ++i)
        {
            if(mp[u][i] == -1) continue;
            k = dis[i];
            if(dis[i] == -1) dis[i] = max(mp[u][i],dis[u]);
            else  dis[i] = min(dis[i],max(dis[u],mp[u][i]));
            if(k == dis[i]) continue;
            if(!vis[i])
            {
                q.push(i);
                vis[i] = 1;
            }
        }
    }
}

int main()
{
    int t,u,v,w,i,j;
    scanf("%d",&t);
    for(j = 1; j <= t; ++j)
    {
        printf("Case %d:\n",j);
        scanf("%d %d",&n,&m);
        tp = 0;
        memset(mp,-1,sizeof(mp));
        for(i = 0; i < m; ++i)
        {
            scanf("%d %d %d",&u,&v,&w);
            mp[u][v] = mp[v][u] = (mp[u][v] == -1)? w: min(w,mp[u][v]);
        }
        scanf("%d",&s);
        SPFA();
        for(i = 0; i < n; ++i)
        {
            if(dis[i] == -1) puts("Impossible");
            else printf("%d\n",dis[i]);
        }
    }
    return 0;
}