「TJOI2019」大中锋的游乐场

题目链接

问题分析

比较明显的最短路模型。需要堆优化的dij。建图的时候注意细节就好。

参考程序

#include <bits/stdc++.h>
#define LL long long
//#define DEBUG
using namespace std;

const int Maxn = 10010;
const int Maxm = 100010;
const int Maxk = 12;
struct edge {
	int To, Next, Cost;
};
edge Edge[ Maxm << 1 ];
int Start[ Maxn ], Used;
int n, m, k, Tag[ Maxn ], Dis[ Maxn ][ Maxk << 1 ], s, t, Vis[ Maxn ][ Maxk << 1 ];
int DistK;
struct heap {
	int Used, Tree[ Maxn * ( Maxk << 1 ) ], Ref[ Maxn * ( Maxk << 1 ) ];
	void Clear() { Used = 0; return; }
	bool Cmp( int x, int y ) {
		return Dis[ x / DistK ][ x % DistK ] < Dis[ y / DistK ][ y % DistK ];
	}
	bool Empty() { return Used == 0; }
	inline void Swap( int x, int y ) {
		Ref[ Tree[ x ] ] = y;
		Ref[ Tree[ y ] ] = x;
		swap( Tree[ x ], Tree[ y ] );
		return;
	}
	void Insert( int x ) {
		++Used; Tree[ Used ] = x; Ref[ x ] = Used;
		int Temp = Used;
		for( ; Temp > 1; )
			if( Cmp( Tree[ Temp ], Tree[ Temp >> 1 ] ) )
				Swap( Temp, Temp >> 1 ), Temp >>= 1;
			else
				break;
		return;
	}
	void Fresh( int x ) {
		int Temp = Ref[ x ];
		for( ; Temp > 1; )
			if( Cmp( Tree[ Temp ], Tree[ Temp >> 1 ] ) )
				Swap( Temp, Temp >> 1 ), Temp >>= 1;
			else
				break;
		return;
	}
	int Top() { return Tree[ 1 ]; }
	void Pop() {
		Swap( 1, Used ); --Used;
		int Temp = 1;
		for( ; ( Temp << 1 ) <= Used; ) {
			if( ( Temp << 1 | 1 ) > Used ) {
				if( Cmp( Tree[ Temp << 1 ], Tree[ Temp ] ) )
					Swap( Temp, Temp << 1 );
				break;
			}
			if( Cmp( Tree[ Temp << 1 ], Tree[ Temp << 1 | 1 ] ) )
				if( Cmp( Tree[ Temp << 1 ], Tree[ Temp ] ) ) {
					Swap( Temp, Temp << 1 );
					Temp <<= 1;
				}
				else
					break;
			else
				if( Cmp( Tree[ Temp << 1 | 1 ], Tree[ Temp ] ) ) {
					Swap( Temp, Temp << 1 | 1 );
					Temp = Temp << 1 | 1;
				}
				else
					break;
		}
		return;
	}
};
heap Heap;

void Clear() {
	memset( Start, 0, sizeof( Start ) );
	Used = 0;
	memset( Dis, 255, sizeof( Dis ) );
	Heap.Clear();
	return;
}

inline void AddEdge( int x, int y, int z ) {
	Edge[ ++Used ] = ( edge ){ y, Start[ x ], z };
#ifdef DEBUG
	printf( "AddEdge %d -> %d : %d\n", x, y, z );
#endif
	Start[ x ] = Used;
	return;
}

void Init() {
	scanf( "%d%d%d", &n, &m, &k );
	++k;
	for( int i = 1; i <= n; ++i ) scanf( "%d", &Tag[ i ] );
	for( int i = 1; i <= n; ++i ) Tag[ i ] = ( Tag[ i ] == 1 ) ? -1 : 1;
	for( int i = 1; i <= m; ++i ) {
		int x, y, z; scanf( "%d%d%d", &x, &y, &z );
		AddEdge( x, y, z ); AddEdge( y, x, z );
	}
	scanf( "%d%d", &s, &t );
	DistK = k << 1;
	return;
}

void Work() {
	Clear();
	Init();
	Dis[ s ][ k + Tag[ s ] ] = 0;
	if( k + Tag[ s ] < 1 || k + Tag[ s ] >= DistK ) {
		printf( "-1\n" );
		return;
	}
	Heap.Insert( s * DistK + k + Tag[ s ] );
	Vis[ s ][ k ] = 2;
	for( ; !Heap.Empty(); ) {
		int T = Heap.Top();
		Heap.Pop();
		int u = T / DistK;
		Vis[ u ][ T % DistK ] = 1;
#ifdef DEBUG
		printf( "Sol %d %d %d\n", u, T % DistK, Dis[ u ][ T % DistK ] );
#endif
		for( int t = Start[ u ]; t; t = Edge[ t ].Next ) {
			int v = Edge[ t ].To; int p = T % DistK + Tag[ v ];
			if( p < 1 || p >= DistK ) continue;
			if( Vis[ v ][ p ] == 1 ) continue;
			if( Dis[ v ][ p ] == -1 ||
					Dis[ v ][ p ] > Dis[ u ][ T % DistK ] + Edge[ t ].Cost ) {
				Dis[ v ][ p ] = Dis[ u ][ T % DistK ] + Edge[ t ].Cost;
#ifdef DEBUG
				printf( "  Cha %d %d %d\n", v, p, Dis[ v ][ p ] );
#endif
				if( Vis[ v ][ p ] == 2 ) Heap.Fresh( v * DistK + p );
				else {
					Heap.Insert( v * DistK + p );
					Vis[ v ][ p ] = 2;
				}
			}
		}
	}
	int Ans = -1;
	for( int i = 1; i < DistK; ++i )
		if( Dis[ t ][ i ] != -1 && ( Ans == -1 || Ans > Dis[ t ][ i ] ) )
			Ans = Dis[ t ][ i ];
	printf( "%d\n", Ans );
	return;
}

int main() {
	int TestCases; scanf( "%d", &TestCases );
	for( ; TestCases--; ) Work();
	return 0;
}