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 <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <queue> using namespace std; const int MAXN = ;
const int INF = << ; 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 = ; 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 - );
return;
} void dijkstra( int s, int *d, int *p )
{
priority_queue<HeapNode> Q;
for ( int i = ; i <= n; ++i ) d[i] = INF;
d[s] = ;
memset( done, , sizeof(done) );
Q.push( HeapNode( , s ) );
while ( !Q.empty() )
{
HeapNode x = Q.top();
Q.pop();
int u = x.u;
if ( done[u] ) continue;
done[u] = true;
for ( int i = ; 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 = ;
while ( scanf( "%d%d%d", &N, &S, &E ) == )
{
slv.init( N );
scanf( "%d", &M );
for ( int i = ; 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 = ; 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 = -;
int huaned; for ( int i = ; 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 == - )
{
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 ;
}
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