• UVa 11374


    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 <cstdio>
    #include <cstring>
    #include <cstdlib>
    #include <algorithm>
    #include <vector>
    #include <queue>
    
    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<Edge> 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<HeapNode> 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<Edge> 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
    ", 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
    ", huan );
            }
            printf( "%d
    ", ans );
    
        }
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/GBRgbr/p/3307540.html
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