poj 3411 Paid Roads(dfs,可重复访问节点)

#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <set>
#include <map>
#include <vector>
#include <math.h>
#include <string.h>
#include <queue>
#include <string>
#include <stdlib.h>
#define LL long long
#define _LL __int64
#define eps 1e-8
using namespace std;
const int INF = 0x3f3f3f3f;
const int maxn = 110;

struct node
{
	int v,c,p,r;
};
vector <node> edge[20];

int n,m;
int vis[20];
int ans;

void dfs(int u, int cost)
{
	if(cost >= ans)
		return;

	if(u == n)
	{
		if(ans > cost)
			ans = cost;
		return;
	}

	for(int i = 0; i < (int)edge[u].size(); i++)
	{
		int v = edge[u][i].v;
        if ( vis[v] <= 3 ) //搜索的限制条件，避免一个点走过超过3次出现环路。之前没加RE了。
        {
        	vis[v]++;
            if ( vis[edge[u][i].c])
				dfs(v, cost + edge[u][i].p);
            else
				dfs(v, cost + edge[u][i].r);
			vis[v]--;
        }
	}
}

int main()
{
	int a,b,c,p,r;
	while(~scanf("%d %d",&n,&m))
	{
		for(int i = 0; i <= n; i++)
			edge[i].clear();
		for(int i = 0; i < m; i++)
		{
			scanf("%d %d %d %d %d",&a,&b,&c,&p,&r);
			edge[a].push_back((struct node){b,c,p,r});
		}
		memset(vis,0,sizeof(vis));
		ans = INF;
		vis[1] = 1;
		dfs(1,0);
		if(ans == INF)
			printf("impossible\n");
		else printf("%d\n",ans);
	}
	return 0;
}