1107 Social Clusters(30 分)
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:
Ki: hi[1] hi[2] ... hi[Ki]
where Ki (>0) is the number of hobbies, and hi[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
解题思路:这题是用并查集,我们用course记录课程第一次出现的人的编号,然后后面的人出现的人的编号跟这个课程第一次出现的人的编号Combine一下就好了,然后我们就从1到n去找是集合的代表元并加1,然后我们再从1到n中看一下加的数量,如果数量不为0,就说明是一个圈,然后我们要统计有多少个圈,然后根据题目要求,从大到小排序,然后输出答案就好。(并查集可以看看https://blog.csdn.net/Imagirl1/article/details/82353349)。
#include<bits/stdc++.h>
using namespace std;
vector<int>father,isroot;
//并查集
int find(int x)
{
while(x!=father[x])
x=father[x];
return x;
}
void Combine(int a,int b)
{
int fa1=find(a);
int fa2=find(b);
if(fa1!=fa2)
father[fa1]=fa2;
}
bool cmp(int a,int b)
{
return a>b;
}
int main(void)
{
int n,m;
scanf("%d",&n);
int course[1001]={0};//初始化为0
isroot.resize(n+1);//统计最父亲节点的人数的数量
father.resize(n+1);
for(int i=1;i<=n;i++)
{
father[i]=i;//都初始化为自己
}
for(int i=1;i<=n;i++)
{
scanf("%d:",&m);
int t;
for(int j=0;j<m;j++)
{
scanf("%d",&t);
if(course[t]==0 )
course[t]=i;//course[t]不会变,永远都是第一次出现的位置
Combine(i,course[t]); //合并
}
}
for(int i=1;i<=n;i++)
{
isroot[find(i)]++;//找到最父亲的节点并加一
}
int cnt=0;
for(int i=1;i<=n;i++)
{
if(isroot[i]!=0) cnt++;//统计有多少个圈
}
printf("%d\n",cnt);
sort(isroot.begin(),isroot.end(),cmp);
for(int i=0;i<cnt;i++)
{
printf("%d",isroot[i]);
if(i!=cnt-1) printf(" ");
}
return 0;
}