标签：des style class blog code http
题目链接：
http://poj.org/problem?id=3411
题目：
| Time Limit: 1000MS | Memory Limit: 65536K | |
| Total Submissions: 5080 | Accepted: 1784 |
Description
A network of m roads connects N cities (numbered from 1 toN). There may be more than one road connecting one city with another. Some of the roads are paid. There are two ways to pay for travel on a paid roadi from city ai to city bi:
The payment is Pi in the first case and Ri in the second case.
Write a program to find a minimal-cost route from the city 1 to the city N.
Input
The first line of the input contains the values of N and m. Each of the following m lines describes one road by specifying the values ofai, bi, ci,Pi, Ri (1 ≤ i ≤ m). Adjacent values on the same line are separated by one or more spaces. All values are integers, 1 ≤m, N ≤ 10, 0 ≤ Pi , Ri ≤ 100,Pi ≤ Ri (1 ≤ i ≤ m).
Output
The first and only line of the file must contain the minimal possible cost of a trip from the city 1 to the cityN. If the trip is not possible for any reason, the line must contain the word ‘impossible’.
Sample Input
4 5 1 2 1 10 10 2 3 1 30 50 3 4 3 80 80 2 1 2 10 10 1 3 2 10 50
Sample Output
110
Source
1：如果以前经过c城市，那么就在c城市付费。。
2：如果没有经过，那么就在b城市付费。。
还有注意题目中的数据为m<10，所以每个点最多走3次。。
因为成环的话那么最少3个点，则最少3路。所以最多走3次。。。
故应用int vis[ manx]。。。
然后dfs回溯。。。
所以代码为：
#include<iostream>
#include<cstdio>
#include<cstring>
#define INF 0x3f3f3f3f
const int maxn=10+10;
int vis[maxn];
int min_cost,fee;
int n,m;
struct node
{
int a,b,c,p,r;
}e[maxn];
void dfs(int x,int fee)
{
if(x==n&&min_cost>fee)
{
min_cost=fee;
return;
}
if(x==n)
return;
for(int i=1;i<=m;i++)
{
if(e[i].a==x&&vis[e[i].b]<3)
{
vis[e[i].b]++;
if(vis[e[i].c])
dfs(e[i].b,fee+e[i].p);
else
dfs(e[i].b,fee+e[i].r);
vis[e[i].b]--;
}
}
}
int main()
{
while(scanf("%d %d",&n,&m)!=EOF)
{
memset(vis,0,sizeof(vis));
min_cost=INF;
for(int i=1;i<=m;i++)
{
scanf("%d%d%d%d%d",&e[i].a,&e[i].b,&e[i].c,&e[i].p,&e[i].r);
}
vis[1]=1;
dfs(1,0);
if(min_cost!=INF)
printf("%d\n",min_cost);
else
printf("impossible\n");
}
return 0;
}
标签：des style class blog code http
原文地址：http://blog.csdn.net/u014303647/article/details/30868237
