#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
const int MAXN=1e2+7;
int a[MAXN][MAXN]; 
template <typename _TP>
inline void read(_TP &X){
	char ch=0;int w;X=0;
	while(!isdigit(ch)){w=ch=='-';ch=getchar();}
	while(isdigit(ch)){X=(X<<1)+(X<<3)+(ch^48);ch=getchar();}
	X=w?-X:X; 
}
inline int minn(const int a,const int b){
	return a<b?a:b; 
}
int main(){
	//freopen("a.out","w",stdout);
	int x,y,z,sum,opt=0,num=0,cnt=0;
	while(true){
		read(x);read(y);
		if(!x && !y)break;
		memset(a,0x3f,sizeof(a));
		num=0;sum=0;
		while(true){
			a[x][y]=1;
			read(x);read(y);				//这里可能需要离散化一下数据 	
			if(!x && !y)break;				//但是这个题可能不需要 
		}
		for(int k=1;k<=100;k++){
			for(int i=1;i<=100;i++){
				for(int j=1;j<=100;j++){
					a[i][j]=minn(a[i][k]+a[k][j],a[i][j]);
				}
			}
		}
		for(int i=1;i<=100;i++){
			for(int j=1;j<=100;j++){
				if(a[i][j]!=0x3f3f3f3f && i!=j){
					num++;
					sum+=a[i][j];
//					printf("%d -> %d = %d \n",i,j,a[i][j]);
//					cout<<num<<"\n";	
				}
			}
		}
//		cout<<"***************\n"<<"num:"<<num<<"\nsum:"<<sum<<"\n***************\n";
		printf("Case %d: average length between pages = %.3lf clicks\n",++cnt,1.0*sum/num);
	}
	return 0;
}

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
const int MAXN=1e2+7;
int a[MAXN][MAXN]; 
template <typename _TP>
inline void read(_TP &X){
	char ch=0;int w;X=0;
	while(!isdigit(ch)){w=ch=='-';ch=getchar();}
	while(isdigit(ch)){X=(X<<1)+(X<<3)+(ch^48);ch=getchar();}
	X=w?-X:X; 
}
inline int minn(const int a,const int b){
	return a<b?a:b; 
}
int main(){
	//freopen("a.out","w",stdout);
	int x,y,z,sum,opt=0,num=0,cnt=0;
	while(true){
		read(x);read(y);
		if(!x && !y)break;
		if(opt)cout<<'\n';
		else opt=1;
		memset(a,0x3f,sizeof(a));
		num=0;sum=0;
		while(true){
			a[x][y]=1;
			read(x);read(y);				//这里可能需要离散化一下数据 	
			if(!x && !y)break;				//但是这个题可能不需要 
		}
		for(int k=1;k<=100;k++){
			for(int i=1;i<=100;i++){
				for(int j=1;j<=100;j++){
					a[i][j]=minn(a[i][k]+a[k][j],a[i][j]);
				}
			}
		}
		for(int i=1;i<=100;i++){
			for(int j=1;j<=100;j++){
				if(a[i][j]!=0x3f3f3f3f && i!=j){
					num++;
					sum+=a[i][j];
//					printf("%d -> %d = %d \n",i,j,a[i][j]);
//					cout<<num<<"\n";	
				}
			}
		}
//		cout<<"***************\n"<<"num:"<<num<<"\nsum:"<<sum<<"\n***************\n";
		printf("Case %d: average length between pages = %.3lf clicks",++cnt,1.0*sum/num);
	}
	return 0;
}

两份代码只有

if(opt)cout<<'\n';
		else opt=1;

有不同，这句话旨在让最后一行不输出空行 加了这段代码的WA了
直接输出的（第一份代码）A了
很奇怪，冥思苦想了半天也不知道哪里出了问题。