When register on a social network, you are always asked to specify your hobbies in order to find some potential friends with the same hobbies. A "social cluster" is a set of people who have some of their hobbies in common. You are supposed to find all the clusters.
Input Specification:
Each input file contains one test case. For each test case, the first line contains a positive integer N (<=1000), the total number of people in a social network. Hence the people are numbered from 1 to N. Then N lines follow, each gives the hobby list of a person in the format:
K~i~: h~i~[1] h~i~[2] ... h~i~[K~i~]
where K~i~ (>0) is the number of hobbies, and h~i~[j] is the index of the j-th hobby, which is an integer in [1, 1000].
Output Specification:
For each case, print in one line the total number of clusters in the network. Then in the second line, print the numbers of people in the clusters in non-increasing order. The numbers must be separated by exactly one space, and there must be no extra space at the end of the line.
Sample Input:
8
3: 2 7 10
1: 4
2: 5 3
1: 4
1: 3
1: 4
4: 6 8 1 5
1: 4
Sample Output:
3
4 3 1思路：
有n个人，每个人喜欢k个活动，如果两个人有任意一个活动相同，就称为他们处于同一个社交网络。求这n个人一共形成了多少个社交网络。
并查集！
C++：
#include "cstdio"
#include "algorithm"
using namespace std;
const int N=1010;
int father[N];//存放父亲结点
int isRoot[N]={0};
int course[N]={0};
//查找x所在集合的根结点
int findFather(int x){
int a=x;
while (x!=father[x])
{
x=father[x];
}
//路径压缩
while (a!=father[a])
{
int z=a;
a=father[a];
father[z]=x;
}
return x;
}
//合并ab所在集合
void Union(int a,int b){
int faA=findFather(a);
int fbB=findFather(b);
if (faA!=fbB)
{
father[faA]=fbB;
}
}
void init(int n){
for(int i=1;i<=n;i++){
father[i]=i;
}
}
bool cmp(int a,int b){
return a>b;
}
int main(){
int n,k,h;
scanf("%d",&n);
init(n);
for(int i=1;i<=n;i++){
scanf("%d:",&k);
for(int j=0;j<k;j++){
scanf("%d",&h);
if(course[h]==0){
course[h]=i;
}
Union(i,findFather(course[h]));
}
}
for(int i=1;i<=n;i++){
isRoot[findFather(i)]++;
}
int ans=0;
for(int i=1;i<=n;i++){
if(isRoot[i]!=0){
ans++;
}
}
printf("%d\n",ans);
sort(isRoot+1,isRoot+n+1,cmp);
for(int i=1;i<=ans;i++){
printf("%d",isRoot[i]);
if(i<ans)printf(" ");
}
return 0;
}