1030. Travel Plan (30)

1030. Travel Plan (30)

时间限制

400 ms

内存限制

65536 kB

代码长度限制

16000 B

判题程序

Standard

作者

CHEN, Yue

A traveler's map gives the distances between cities along the highways, together with the cost of each highway. Now you are supposed to write a program to help a traveler to decide the shortest path between his/her starting city and the destination. If such a shortest path is not unique, you are supposed to output the one with the minimum cost, which is guaranteed to be unique.

Input Specification:

Each input file contains one test case. Each case starts with a line containing 4 positive integers N, M, S, and D, where N (<=500) is the number of cities (and hence the cities are numbered from 0 to N-1); M is the number of highways; S and D are the starting and the destination cities, respectively. Then M lines follow, each provides the information of a highway, in the format:

City1 City2 Distance Cost

where the numbers are all integers no more than 500, and are separated by a space.

Output Specification:

For each test case, print in one line the cities along the shortest path from the starting point to the destination, followed by the total distance and the total cost of the path. The numbers must be separated by a space and there must be no extra space at the end of output.

Sample Input

4 5 0 3 0 1 1 20 1 3 2 30 0 3 4 10 0 2 2 20 2 3 1 20

Sample Output

0 2 3 3 40

这道题我又给做复杂了，我用dijistra算法的得到多条最短路径，再用DFS根据cost择最优路径，结果最后两个测试点没过去。

网上看大神的做法是直接在dijistra算法上添加cost择优。与1018 Public bike不太一样，那道题涉及出来和回去两个方向，实质是两条路，所以需要存起来。贴一个自己版本的和一个网上看到比较好的版本。

#include<iostream>
#include<fstream>
#include<string>
#include<algorithm>
#include<vector>
#include<queue>
#define inf 1000000
using namespace std;
struct NODE
{
	int dis;
	int cost;
	NODE():dis(inf),cost(inf){};
};
int mincost = inf;
vector<int>bestway;

vector<vector<int>>pre;
vector<vector<NODE>>graph;
vector<int>nowway;
void DFS(int i,int nowcost)
{
	nowway.push_back(i);
	if (pre[i][0] == -1)
	{   
		if (nowcost < mincost)
		{
			bestway = nowway;
			mincost = nowcost;
		}
		return;
	}
	else
	{
		
		for (int j = 0; j < pre[i].size(); j++)
		{
			//nowcost += graph[i][pre[i][j]].cost;
			DFS(pre[i][j], nowcost+ graph[i][pre[i][j]].cost);
			nowway.pop_back();
		}

	}
}
int main()
{
	//ifstream fin("Text.txt");
	
	int city, road, start, des;
	cin >> city >> road >> start >> des;
	//struct NODE graph[500][500];
	pre.resize(city);
	graph.resize(city);
	int i,j,a,b,x,y;
	for (i = 0; i < city; i++)
		graph[i].resize(city);
	//vector<int>pre(city,-1);
	vector<int>dis(city, inf);
	vector<int>fee(city, inf);
	vector<int>flag(city, 0);
	
	vector<int>list;
	
	for (i = 0; i < road; i++)
	{
		cin >> a >> b>>x>>y;
		graph[a][b].dis = x;
		graph[a][b].cost = y;
		graph[b][a].dis = x;
		graph[b][a].cost = y;
	}
	for (i = 0; i < city; i++)
	{
		graph[i][i].cost = 0;
		graph[i][i].dis = 0;
	}
	for (i = 0; i < city; i++)
	{
		dis[i] = graph[start][i].dis;
		fee[i] = graph[start][i].cost;

	}
	pre[start].push_back(-1);
	int index=-1,min=inf;
	while (1)
	{
		index = -1, min = inf;
		list.clear();
			for (i = 0; i < city; i++)
			{
				if (flag[i] == 0 && dis[i] < min)
				{
					min = dis[i];
					index = i;
					list.clear();
					list.push_back(i);
				}
				else if (flag[i] == 0 && dis[i] == min)
				{
					list.push_back(i);
				}

			}
			if (list.empty())break;
			for (i = 0; i < list.size(); i++)
			{
				index = list[i];
				flag[index]=1;
				for ( j = 0; j < city; j++)
				{
					if ( graph[index][j].dis < inf && flag[j] == 0)
					{
						if (dis[index] + graph[index][j].dis  < dis[j])
						{
							dis[j] = dis[index] + graph[index][j].dis
								;
							pre[j].clear();
							pre[j].push_back(index);
						}
						else if (dis[index] + graph[index][j].dis == dis[j])
						{
							pre[j].push_back(index);
						}
					}
				}
			}

	}
	//DFS
	//vector<int>nowway;
	DFS(des,0);
	//cout << start;
	for (i = bestway.size() - 1; i >= 0; i--)
		cout<< bestway[i]<<" ";
	cout << bestway.size() << " " << mincost;
	//cin.get();
	return 0;
}

兔子哥的

/*2015.7.23cyq*/
#include <iostream>
#include <vector>
#include <algorithm>
#include <fstream>
using namespace std;

//ifstream fin("case1.txt");
//#define cin fin

const int MAX=2147483647;
struct city{
	int num;
	int distance;
	int cost;
	city(int n,int td,int tc):num(n),distance(td),cost(tc){}

	bool operator < (const city &a)const{
		if(distance<a.distance)
			return true;
		else if(distance ==a.distance){
			if(cost<a.cost)
				return true;
		}
		return false;
	}
};
struct road{
	int length;
	int cost;
	road(int l,int c):length(l),cost(c){}
};


int main(){
	int N,M,S,D;
	cin>>N>>M>>S>>D;
	vector<vector<road> > roads(N,vector<road>(N,road(-1,-1)));

	int a,b,c,d;
	while(M--){
		cin>>a>>b>>c>>d;
		roads[a][b].length=c;
		roads[b][a].length=c;
		roads[a][b].cost=d;
		roads[b][a].cost=d;
	}
	vector<city> UD;
	for(int i=0;i<N;i++){
		if(i!=S)
			UD.push_back(city(i,MAX,MAX));
	}
	city cur=city(S,0,0);
	vector<int> preCity(N);//前驱数组，用于输出路径
	preCity[S]=-1;
	while(cur.num!=D){
		for(auto it=UD.begin();it!=UD.end();++it){
			if(roads[cur.num][(*it).num].length>0){//有路
				int tmpL=cur.distance+roads[cur.num][(*it).num].length;
				if(tmpL<(*it).distance){
					(*it).distance=tmpL;
					(*it).cost=cur.cost+roads[cur.num][(*it).num].cost;
					preCity[(*it).num]=cur.num;
				}else if(tmpL==(*it).distance){
					int tmpC=cur.cost+roads[cur.num][(*it).num].cost;
					if(tmpC<(*it).cost){
						(*it).cost=tmpC;
						preCity[(*it).num]=cur.num;
					}
				}
			}
		}
		sort(UD.begin(),UD.end());
		cur=UD[0];
		UD.erase(UD.begin());
	}
	vector<int> result;
	int k=D;
	while(k!=S){//逆序压入路径，不包含起点
		result.push_back(k);
		k=preCity[k];
	}

	cout<<S;
	for(auto it=result.rbegin();it!=result.rend();++it)
		cout<<" "<<*it;
	cout<<" "<<cur.distance<<" "<<cur.cost<<endl;
	return 0;
}