1018. Public Bike Management (30)

考察最短路，以及记录相同长度最短路，然后遍历选择最优最短路

#include
#include
#include
#include
using namespace std;

#define INF 0x6FFFFFFF
int Cmax, n, Sp, m;
typedef struct Edge
{
	int v, dis;
	Edge(int _v, int _dis):v(_v),dis(_dis){}
}Edge;

typedef struct Node
{
	int c, dis;
}Node;
vector> edge;
vector city;
vector> allPath;
vector visited;

vector bestPath;
int minSend = INF;
int minCollect = INF;
vector possiblePath;
void FindBestPath(int u)
{
	possiblePath.push_back(u);
	if(u == 0)
	{//find the end
		int send = 0;
		int collect = 0;
		for(int i = possiblePath.size()-1; i >= 0; --i)
		{
			int t = possiblePath[i];
			if(city[t].c > Cmax/2)
				collect += city[t].c - Cmax/2;
			else if(city[t].c < Cmax/2)
			{
				collect -= (Cmax/2-city[t].c);
				if(collect < 0) send -=collect, collect=0;
			}
		}
		if(send < minSend) minSend=send, minCollect=collect, bestPath=possiblePath;
		else if(send == minSend && collect < minCollect) minCollect=collect, bestPath=possiblePath;
		return;
	}
	for(int i = 0; i < allPath[u].size(); ++i)
	{
		FindBestPath(allPath[u][i]);
		possiblePath.pop_back();
	}
}
int FindMin()
{
	int mmin = INF;
	int index = -1;
	for(int i = 0; i <= n; ++i)
	{
		if(city[i].dis < mmin && !visited[i])
		{
			mmin = city[i].dis;
			index = i;
		}
	}
	return index;
}
void Dijkstra(int s, int t)
{
	allPath.clear();
	allPath.resize(n+1);
	/*for(int i = 0; i <= n; ++i)
		allPath[i].push_back(-1);*/
	visited.assign(n+1, false);
	for(int i = 0; i <= n; ++i)
		city[i].dis = INF;
	city[0].dis = 0;
	while(true)
	{
		int u = FindMin();
		if(u==-1) return;
		visited[u] = true;
		for(int i = 0; i < edge[u].size(); ++i)
		{
			int v = edge[u][i].v;
			if(!visited[v])
			{
				int dis = edge[u][i].dis;
				if(city[v].dis > city[u].dis+dis)
				{
					allPath[v].clear();
					city[v].dis = city[u].dis+dis;
					allPath[v].push_back(u);
				}
				else if(city[v].dis == city[u].dis+dis)
				{
					allPath[v].push_back(u);
				}
			}
		}
	}

}
int main()
{
	scanf("%d%d%d%d",&Cmax,&n,&Sp,&m);
	city.clear();
	city.resize(n+1);
	for(int i = 1; i <= n; ++i)
	{
		scanf("%d",&city[i].c);
		city[0].c = Cmax/2;
	}
	edge.clear();
	edge.resize(n+1);
	for(int i = 0; i < m; ++i)
	{
		int a, b, c;
		scanf("%d%d%d",&a,&b,&c);
		edge[a].push_back(Edge(b,c));
		edge[b].push_back(Edge(a,c));
	}
	
	//end of input
	//1. using dijkstra find all the possible solution
	Dijkstra(0, Sp);
	//2. enumerate all possible path and record the best one
	FindBestPath(Sp);
	//output the best solution
	printf("%d 0",minSend);
	for(int i = bestPath.size()-2; i >= 0; --i)
		printf("->%d",bestPath[i]);
	printf(" %d\n", minCollect);
	return 0;
}