ZJU PAT 1018

Solar-Rain 2013-10-07 11:31:55

一个case过不去，求救

题目链接： http://pat.zju.edu.cn/contests/pat-a-practise/1018

#include <iostream>

using namespace std;



const int INF=9999999;

const int MAXN=512;

int S[MAXN];

int R[MAXN][MAXN];

int Path[2][MAXN];

bool visited[MAXN];

int Cmax,N,Sp,M;

//Dij先求出最短路径

int Dijkstra(int v,int N)

{

	int path[MAXN];

	int distance[MAXN];

	for(int i=0;i<=N;++i)distance[i]=R[0][i],path[i]=0;	

	for(int i=1;i<=N;++i)

	{

		int min=INF;

		int p;

		for(int j=1;j<=N;++j)

		{

			if(min>distance[j]&&visited[j]==false)

			{	

				min=distance[j];

				p=j;

			}

		}

		visited[p]=true;

		for(int j=1;j<=N;++j)

		{

			if(distance[j]>distance[p]+R[p][j])

			{

				path[j]=p;

				distance[j]=distance[p]+R[p][j];

			}

		}

	}

	return distance[v];

}

//DFS遍历的同时计算最优路径

int DFS(int v,int N,int &distance,int shortest,int &sum,int &mintake,int &minsend,int &send,int &take)

{

	if(v==Sp&&distance==shortest)

	{

		if(sum<mintake)

		{

			take=sum;

			mintake=take;

			minsend=send;

			for(int k=0;k<=N;++k)

			{

				Path[0][k]=Path[1][k];

			}

			return 0;

		}

		if(sum==mintake&&send<minsend)

		{

			take=sum;

			mintake=take;

			minsend=send;

			for(int k=0;k<=N;++k)

			{

				Path[0][k]=Path[1][k];

			}

			return 0;

		}

	}

	int i;

	for(i=1;i<=N;++i)

	{

		if(v==0)sum=0,distance=0,send=0,take=0;

		if(visited[i]==false&&R[v][i]<INF)

		{

			distance+=R[v][i];

			if(distance>shortest)

			{

				distance-=R[v][i];

				continue;

			}

			int t1=sum,t2=send;

			sum+=S[i]-Cmax/2;

			if(sum<0)

			{

				send+=sum*(-1);

				sum=0;

			}

			visited[i]=true;	

			Path[1][i]=v;

			DFS(i,N,distance,shortest,sum,mintake,minsend,send,take);

			visited[i]=false;

			distance-=R[v][i];			

			sum=t1;

			send=t2;

		}

	}

}

///////////////////////////

int main()

{

	freopen("in.txt","r",stdin);

	freopen("out.txt","w",stdout);

	for(int i=0;i<MAXN;++i)

		for(int j=0;j<MAXN;++j)

			S[i]=-1,R[i][j]=INF;	

	scanf("%d%d%d%d",&Cmax,&N,&Sp,&M);

	for(int i=1;i<=N;++i)

		scanf("%d",&S[i]);

	for(int i=1;i<=M;++i)

	{

		int a,b,t;

		scanf("%d%d%d",&a,&b,&t);

		R[a][b]=R[b][a]=t;

	}

//输入完成



	int shortest=Dijkstra(Sp,N);

	for(int i=0;i<=N;++i)

		visited[i]=false;

	int distance=0,sum=0,minsend=INF,mintake=INF;

	int send=0,take=0;

	DFS(0,N,distance,shortest,sum,mintake,minsend,send,take);

//输出

	int stack[MAXN];

	int p=-1;

	Path[0][0]=-1;

	int k=Sp;

	while(Path[0][k]!=-1)

	{

		stack[++p]=k;

		k=Path[0][k];

	}

	printf("%d 0",minsend);

	while(p!=-1)

		printf("->%d",stack[p--]);

	printf(" %d",mintake);

	return 0;

}