poj1847 最短路

 1 //Accepted    188 KB    32 ms
 2 //spfa 最短路
 3 //每个intersection到第一个连接点是不要switch的
 4 //到其他的intersection要switch一次
 5 #include <cstdio>
 6 #include <cstring>
 7 #include <iostream>
 8 #include <queue>
 9 #include <cmath>
10 #include <algorithm>
11 using namespace std;
12 /**
13   * This is a documentation comment block
14   * 如果有一天你坚持不下去了，就想想你为什么走到这儿！
15   * @authr songt
16   */
17 const int imax_n = 105;
18 const int inf = 100000000;
19 int a[imax_n][imax_n];
20 bool vis[imax_n];
21 int dis[imax_n];
22 int n;
23 bool relax(int u,int v,int c)
24 {
25     if (dis[v]>dis[u]+c)
26     {
27         dis[v]=dis[u]+c;
28         return true;
29     }
30     return false;
31 }
32 queue<int > Q;
33 void spfa(int src)
34 {
35     while (!Q.empty()) Q.pop();
36     memset(vis,0,sizeof(vis));
37     for (int i=1;i<=n;i++)
38     dis[i]=inf;
39     dis[src]=0;
40     Q.push(src);
41     vis[src]=true;
42     while (!Q.empty())
43     {
44         int pre=Q.front();
45         Q.pop();
46         vis[pre]=false;
47         for (int i=1;i<=n;i++)
48         if (relax(pre,i,a[pre][i]) && !vis[i])
49         {
50             Q.push(i);
51             vis[i]=true;
52         }
53     }
54 }
55 int start,end;
56 int main()
57 {
58     int x,y,cnt;
59     while (scanf("%d%d%d",&n,&start,&end)!=EOF)
60     {
61         for (int i=1;i<=n;i++)
62         {
63             for (int j=1;j<=n;j++)
64             a[i][j]=inf;
65             a[i][i]=0;
66         }
67         for (int i=1;i<=n;i++)
68         {
69             scanf("%d",&cnt);
70             if (cnt!=0)
71             {
72                 scanf("%d",&x);
73                 a[i][x]=0;
74                 cnt--;
75             }
76             for (int j=0;j<cnt;j++)
77             {
78                 scanf("%d",&x);
79                 a[i][x]=1;
80             }
81         }
82         //printf("gg\n");
83         spfa(start);
84         if (start==end) dis[end]=1;
85         if (dis[end]==inf) printf("-1\n");
86         else
87         printf("%d\n",dis[end]);
88     }
89     return 0;
90 }