https://www.luogu.org/problemnew/show/P2047

https://www.lydsy.com/JudgeOnline/problem.php?id=1491

也可以用floyed做掉

 1 #include<cstdio>
 2 #include<algorithm>
 3 #include<cstring>
 4 #include<vector>
 5 using namespace std;
 6 #define fi first
 7 #define se second
 8 #define
 
 mp make_pair
 9 #define pb push_back
10 typedef long long ll;
11 typedef unsigned long long ull;
12 typedef pair<int,int> pii;
13 ll n,m;
14 ll a[110][110],d[110][110];
15 ll n1[110][110];//最短路計數
16 double an[110];
17 int main()
18 {
19     ll i,j,k,x,y,z;
20     scanf("%lld%lld",&n,&m);
 
21     memset(a,0x3f,sizeof(a));
22     for(i=1;i<=n;++i)
23         a[i][i]=0;
24     for(i=1;i<=m;++i)
25     {
26         scanf("%lld%lld%lld",&x,&y,&z);
27         a[x][y]=a[y][x]=min(a[x][y],z);
28     }
29     memcpy(d,a,sizeof(d));
30     for(i=1;i<=n;++i)
31         for
 
(j=1;j<=n;++j)
32             n1[i][j]=1;
33     for(k=1;k<=n;++k)
34         for(i=1;i<=n;++i)
35             for(j=1;j<=n;++j)
36                 if(i!=k&&i!=j&&k!=j)
37                 {
38                     if(d[i][j]>d[i][k]+d[k][j])
39                     {
40                         d[i][j]=d[i][k]+d[k][j];
41                         n1[i][j]=n1[i][k]*n1[k][j];
42                     }
43                     else if(d[i][j]==d[i][k]+d[k][j])
44                     {
45                         n1[i][j]+=n1[i][k]*n1[k][j];
46                     }
47                 }
48     //for(i=1;i<=n;++i)
49     //    for(j=1;j<=n;++j)
50     //        printf("1t%lld %lld %lld %lld\n",i,j,d[i][j],n1[i][j]);
51     for(i=1;i<=n;++i)
52     {
53         for(j=1;j<=n;++j)
54             for(k=1;k<=n;++k)
55                 if(i!=j&&j!=k&&i!=k)
56                 {
57                     if(d[j][i]+d[i][k]==d[j][k])
58                     {
59                         an[i]+=double(n1[j][i])*n1[i][k]/n1[j][k];
60                     }
61                 }
62         printf("%.3f\n",an[i]);
63     }
64     return 0;
65 }