【PAT】1107. Social Clusters (30)

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:

83: 2 7 101: 42: 5 31: 41: 31: 44: 6 8 1 51: 4

Sample Output:

3
4 3 1
分析：简单的并查集问题。
#include <iostream>#include <vector>#include <algorithm>#include <queue>#include <set>using namespace std;struct node{vector<int> sons;};vector<node> hobby(1001);vector<int> par;vector<int> Rank;vector<int> num;void init(int n){par.resize(n);Rank.resize(n,0);num.resize(n);int i;for(i=0; i<n; i++){par[i] = i;num[i] = 1;}}int find(int x){if(x==par[x]){return x;}return par[x] = find(par[x]);}bool same(int a, int b){if(find(a) == find(b)){return true;}else{return false;}}int maxNum;bool cmp(int a, int b){return a>b;}void unite(int a, int b){int x = find(a);int y = find(b);if(x==y){return ;}maxNum--;if(Rank[x]<Rank[y]){par[x] = y;num[y] += num[x];}else{par[y] = x;num[x] += num[y];if(Rank[x] == Rank[y]){Rank[x]++;}}}int main(int argc, char** argv) {int N;scanf("%d",&N);init(N);int tmp, id, i;maxNum = N; for(i=0; i<N; i++){scanf("%d:",&tmp);for(int j=0; j<tmp; j++){scanf("%d",&id);hobby[id].sons.push_back(i);}}  for(i=0; i<=1000; i++){ if(hobby[i].sons.size()!=0){ int a = hobby[i].sons[0]; for(int j=1; j<hobby[i].sons.size(); j++){ int b = hobby[i].sons[j]; unite(a,b); }  }  }set<int> s;for(i=0; i<N; i++){int fa = find(i);s.insert(fa);}set<int>::iterator it = s.begin();vector<int> final;for(; it!=s.end(); it++){int fa = find(*it);final.push_back(num[fa]);}printf("%d\n",maxNum);sort(final.begin(), final.end(), cmp);for(i=0; i<final.size(); i++){if(i==0){printf("%d",final[i]);}else{printf(" %d",final[i]);}}printf("\n");return 0;}