裸的Floyd,或许。。。应该注意一下怎么算平均值?
#include <cstdio>
#include <iostream>
#include <string>
#include <map>
#define inf 0x3f3f3f3f
using namespace std;
int dis[1000][1000];
int main()
{
//freopen("ztest.txt","r",stdin);
int a, b, c, d, n, t = 1;
double sum;
while(scanf("%d%d", &a, &b) && (a||b))
{
sum = 0;
for(int i = 0; i < 150; i++)
for(int j = 0; j < 150; j++)
dis[i][j] = (i==j ? 0:inf);
map<int, int> mp;
int u = 0;
if(!mp.count(a)) mp[a] = u++;
if(!mp.count(b)) mp[b] = u++;
c = mp[a];
d = mp[b];
dis[c][d] = 1;
while(scanf("%d%d", &a, &b) && (a||b))
{
if(!mp.count(a)) mp[a] = u++;
if(!mp.count(b)) mp[b] = u++;
c = mp[a];
d = mp[b];
dis[c][d] = 1;
}
n = u;
for(int k = 0; k < n; k++)
for(int i = 0; i < n; i++)
for(int j = 0; j < n; j++)
if(dis[i][k] < inf && dis[k][j] < inf)
dis[i][j] = min(dis[i][j], dis[i][k]+dis[k][j]);
for(int i = 0; i < n; i++)
for(int j = 0; j < n; j++)
sum += dis[i][j];
printf("Case %d: average length between pages = %.3lf clicks\n",t++,sum/((u-1)*u));
}
return 0;
}