LightOJ 1002 Country Roads

http://lightoj.com/volume_showproblem.php?problem=1002

求最长路径的最小值，用优先队列的dijkstra。

 

#include<cstdio>

#include<cstring>

#include<cstdlib>

#include<queue>

#include<algorithm>

using namespace std;



const int MAXN = 1 << 9;

int dist[MAXN], g[MAXN][MAXN];

int n, m, t;

const int inf = 0x3f3f3f3f;

typedef pair<int, int> pii;



void ReadGragh()

{

    for( int i = 0; i < n; i ++)

        for( int j = 0; j < n; j ++)

        {

            if( i != j)

                g[i][j] = inf;

            else

                g[i][j] = 0;

        }

    while( m --)

    {

        int u, v, w;

        scanf( "%d%d%d", &u, &v, &w);

        if( g[u][v] > w)

            g[u][v] = g[v][u] = w;

    }

    scanf( "%d", &t);

}



void Dijkstra()

{

    priority_queue< pii, vector<pii>, greater<pii> > q;

    for( int i = 0; i < n; i ++)

        dist[i] = inf;

    dist[t] = 0;

    q.push( make_pair(0, t));

    while( !q.empty())

    {

        pii u = q.top(); q.pop();

        int x = u.second;

        if( dist[x] != u.first) continue; //±ÜÃâÖظ´¸üÐÂ

        for( int i = 0; i < n; i ++)

        {

            if( i != x && dist[i] > max(dist[x], g[x][i]) )

            {

                dist[i] = max(dist[x], g[x][i]);

                q.push( make_pair(dist[i], i));

            }

        }

    }

}



int main()

{

    int T, cas;

    scanf( "%d", &T);

    for( cas = 1; cas <= T; cas ++)

    {

        scanf( "%d%d", &n, &m);

        ReadGragh();

        Dijkstra();

        printf( "Case %d:\n", cas);

        for( int i = 0; i < n; i ++)

        {

            if( dist[i] == inf)

                printf( "Impossible\n");

            else

                printf( "%d\n", dist[i]);

        }

    }

    return 0;

}