UVa 11374 - Airport Express ( dijkstra预处理 )

起点和终点各做一次单源最短路, d1[i], d2[i]分别代表起点到i点的最短路和终点到i点的最短路，枚举商业线车票cost(a, b);  ans = min( d1[a] + cost(a, b) + d2[b] );

#include 
#include 
#include 
#include 
#include 
#include 

using namespace std;

const int MAXN = 1010;
const int INF  = 1 << 22;

struct HeapNode
{
    int d, u;
    HeapNode() { }
    HeapNode( int _d, int _u ): d(_d), u(_u) { }
    bool operator<( const HeapNode& rhs ) const
    {
        return d > rhs.d;
    }
};

struct Edge
{
    int from, to, dist;
    Edge() { }
    Edge( int f, int t, int d ) : from(f), to(t), dist(d) { }
};

int N, S, E;

struct Dijkstra
{
    int n, m;
    vector edges;
    vector<int> G[MAXN];
    bool done[MAXN];
    int d1[MAXN];
    int d2[MAXN];
    int p1[MAXN];
    int p2[MAXN];

    void init( int n )
    {
        this->n = n;
        for ( int i = 0; i <= n; ++i ) G[i].clear();
        edges.clear();
        return;
    }

    void AddEdge( int from, int to, int dist )
    {
        edges.push_back( Edge( from, to, dist ) );
        m = edges.size();
        G[from].push_back(m - 1);
        return;
    }
    
    void dijkstra( int s, int *d, int *p )
    {
        priority_queue Q;
        for ( int i = 0; i <= n; ++i ) d[i] = INF;
        d[s] = 0;
        memset( done, 0, sizeof(done) );
        Q.push( HeapNode( 0, s ) );
        while ( !Q.empty() )
        {
            HeapNode x = Q.top();
            Q.pop();
            int u = x.u;
            if ( done[u] ) continue;
            done[u] = true;
            for ( int i = 0; i < G[u].size(); ++i )
            {
                Edge& e = edges[ G[u][i] ];
                if ( d[e.to] > d[u] + e.dist )
                {
                    d[e.to] = d[u] + e.dist;
                    p[e.to] = G[u][i];
                    Q.push( HeapNode( d[e.to], e.to ) );
                }
            }
        }
        return;
    }

    void Print1( int e )
    {
        if ( e == S )
        {
            printf( "%d", S );
            return;
        }
        Edge& tp = edges[ p1[e] ];
        Print1( tp.from );
        printf( " %d", e );
        return;
    }

    void Print2( int e )
    {
        if ( e == E )
        {
            printf( " %d", E );
            return;
        }
        Edge& tp = edges[ p2[e] ];
        printf( " %d", e );
        Print2( tp.from );
        return;
    }

};

int M, K;
Dijkstra slv;
vector ec;  //经济线路

int main()
{
    //freopen( "UVa_11374.in", "r", stdin );
    //freopen( "UVa_11374.out", "w", stdout );
    int cas = 0;
    while ( scanf( "%d%d%d", &N, &S, &E ) == 3 )
    {
        slv.init( N );
        scanf( "%d", &M );
        for ( int i = 0; i < M; ++i )
        {
            int u, v, cost;
            scanf( "%d%d%d", &u, &v, &cost );
            slv.AddEdge( u, v, cost );
            slv.AddEdge( v, u, cost );
        }
        
        ec.clear();
        scanf( "%d", &K );
        for ( int i = 0; i < K; ++i )
        {
            int u, v, cost;    
            scanf( "%d%d%d", &u, &v, &cost );
            ec.push_back( Edge(u, v, cost) );
        }

            slv.dijkstra( S, slv.d1, slv.p1 );
        slv.dijkstra( E, slv.d2, slv.p2 );

//        for ( int i = 1; i <= N; ++i )
//        {
//            printf("%d %d\n", slv.d1[i], slv.d2[i] );
//        }
        
        int ans = slv.d1[E];
        int huan = -1;
        int huaned;

        for ( int i = 0; i < K; ++i )
        {
            int u = ec[i].from;
            int v = ec[i].to;
            int tmp1 = slv.d1[u] + ec[i].dist + slv.d2[v];
            int tmp2 = slv.d1[v] + ec[i].dist + slv.d2[u];
            if ( tmp1 < ans )
            {
                ans = tmp1;
                huan = u;
                huaned = v;
            }
            if ( tmp2 < ans )
            {
                ans = tmp2;
                huan = v;
                huaned = u;
            }
        }

        if (cas) puts("");
        ++cas;

        if ( huan == -1 ) 
        {
            slv.Print1(E);
            puts("");
            puts("Ticket Not Used");
        }
        else
        {
            slv.Print1(huan);
            slv.Print2(huaned);
            puts("");
            printf( "%d\n", huan );
        }
        printf( "%d\n", ans );

    }
    return 0;
}

 

转载于:https://www.cnblogs.com/GBRgbr/p/3307540.html