图论trainning-part-1 B. A Walk Through the Forest

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <climits>
 7 #include <vector>
 8 #include <queue>
 9 #include <cstdlib>
10 #include <string>
11 #include <set>
12 #define LL long long
13 #define INF 0x3f3f3f
14 using namespace std;
15 const int maxn = 1010;
16 int mp[maxn][maxn],d[maxn],p[maxn];
17 int n,m;
18 bool vis[maxn];
19 void dij(int src){
20     int i,j,temp,index;
21     for(i = 1; i <= n; i++)
22         d[i] = INF;
23     d[src] = 0;
24     memset(vis,false,sizeof(vis));
25     for(i = 0; i < n; i++){
26         temp = INF;
27         for(j = 1; j <= n; j++)
28         if(!vis[j] && d[j] < temp) temp = d[index = j];
29         vis[index] = true;
30         for(j = 1; j <= n; j++)
31             if(!vis[j] && d[j] > d[index]+mp[index][j])
32                 d[j] = d[index] + mp[index][j];
33     }
34 }
35 int dfs(int s){
36     if(p[s]) return p[s];
37     if(s == 2) return 1;
38     int i,sum = 0;
39     for(i = 1; i <= n; i++){
40         if(mp[s][i] < INF && d[s] > d[i]) sum += dfs(i);
41     }
42     p[s]+= sum;
43     return p[s];
44 }
45 int main(){
46     int i,j,u,v,w;
47     while(scanf("%d",&n),n){
48         scanf("%d",&m);
49         for(i = 1; i <= n; i++)
50             for(j = 1; j <= n; j++)
51                 mp[i][j] = INF;
52         for(i = 0; i < m; i++){
53             scanf("%d%d%d",&u,&v,&w);
54             mp[u][v] = mp[v][u] = w;
55         }
56         dij(2);
57         memset(p,0,sizeof(p));
58         printf("%d\n",dfs(1));
59     }
60     return 0;
61 }