PAT (Advanced Level) Practice 1107 Social Clusters (30 分)並查集
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
題意:
給出每個人的愛好,如果兩個人的愛好其中有一項相同,則他們為同一個類,求一共有幾個不同的類,並輸出每個類的人數。
思路:
並查集。
程式碼如下:
#include <cstdio> #include <cstring> #include <algorithm> #include <iostream> #include <vector> #include <map> using namespace std; const int maxn=1005; int a[maxn]; int n; vector<int> h[maxn]; int vis[maxn][maxn]; int num[maxn]; map<int,int>ma; int Find (int x) { if(a[x]==x) { return x; } return a[x]=Find(a[x]); } void unit(int x,int y) { int para=Find(x); int parb=Find(y); if(para!=parb) { a[para]=parb; } } int compare (int a,int b) { return a>b; } int main() { scanf("%d",&n); memset (num,0,sizeof(num)); memset (vis,0,sizeof(vis)); for (int i=0;i<=n;i++) { a[i]=i; } for (int i=1;i<=n;i++) { int x; scanf("%d:",&x); for (int j=0;j<x;j++) { int y; scanf("%d",&y); vis[i][y]=1; h[i].push_back(y); } } for (int i=1;i<=n-1;i++) { for (int k=0;k<h[i].size();k++) { for (int j=i+1;j<=n;j++) { if(vis[j][h[i][k]]) unit(j,i); } } } for (int i=1;i<=n;i++) { a[i]=Find(i); num[a[i]]++; } int cnt=0; for (int i=1;i<=1000;i++) { if(num[i]) { cnt++; } } printf("%d\n",cnt); sort(num,num+1002,compare); for (int i=0;i<cnt;i++) { printf("%d%c",num[i],i==cnt-1?'\n':' '); } return 0; }