7-36 社交网络图中结点的“重要性”计算

dijkstra写多了，法一（dijkstra）：（推荐法二（bfs））

#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
using namespace std;
const int N=1010;
struct node{
	int id,d;
	bool operator <(const node &n1)const{
		if(d==n1.d) return id>n1.id;
		return d>n1.d;
	}
};
int n,m,k;
vector<int>e[N];
priority_queue<node>pq;
int dis[N];
void dijkstra(){
	while(pq.size()){
		node u=pq.top(); pq.pop();
	//	printf("***%d\n",u.id);
		if(dis[u.id]!=1e9) continue;
	//	printf("$%d\n",u.id);
		dis[u.id]=u.d;
		for(int v:e[u.id]){
			if(dis[v]!=1e9) continue;
	//		printf("#%d\n",v);
			pq.push({v,dis[u.id]+1});
		} 
	}
}
int main(){
	scanf("%d%d",&n,&m);
	for(int i=0;i<m;i++){
		int x,y; scanf("%d%d",&x,&y);
		e[x].push_back(y);
		e[y].push_back(x);
	}
	scanf("%d",&k);
	while(k--){
		int num; scanf("%d",&num);
		while(pq.size()) pq.pop();
		//memset(dis,1e9,sizeof(dis)) !!!!!不行不行不行 
	    for(int i=0;i<=n;i++)
	       dis[i]=1e9;
		dis[num]=0;
		for(int x:e[num]){
			pq.push({x,1});
		}
		dijkstra();
		dis[num]=0;
		int ans=0;
		for(int i=1;i<=n;i++){
		//	printf("##%d\n",dis[i]);
			ans+=dis[i];
			if(dis[i]==1e9){
				printf("Cc(%d)=0\n",num); ans=-1; break;
			}
		}
		if(ans!=-1) printf("Cc(%d)=%.2f\n",num,(float)(n-1)/ans);
	}
	return 0;
}

法二：

#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
using namespace std;
const int N=1010;
int n,m,k;
int dis[N],fa[N];
vector<int>e[N];
queue<int>q;
void bfs(){
	while(q.size()){
		int u=q.front(); q.pop();
		if(dis[u]!=1e9) continue;
			dis[u]=dis[fa[u]]+1;
		for(int v:e[u]){
			if(fa[v]) continue;
			q.push(v); fa[v]=u;
		}
	}
}
int main(){
	scanf("%d%d",&n,&m);
	for(int i=0;i<m;i++){
		int x,y; scanf("%d%d",&x,&y);
		e[x].push_back(y);
		e[y].push_back(x);
	}
	scanf("%d",&k);
	while(k--){
		int num; scanf("%d",&num);
	    for(int i=0;i<=n;i++)
	       dis[i]=1e9;
	    memset(fa,0,sizeof(fa));
	    dis[num]=0;
		for(int x:e[num]){
			q.push(x);
			fa[x]=num;
		}
		bfs();
		int ans=0;
		for(int i=1;i<=n;i++){
		//	printf("#%d\n",dis[i]);
			ans+=dis[i];
			if(dis[i]==1e9){
				printf("Cc(%d)=0.00\n",num); ans=-1; break;
			}
		}
		if(ans!=-1) printf("Cc(%d)=%.2f\n",num,(float)(n-1)/ans);
	}
	return 0;
}