PAT--1107. Social Clusters(并查集)

题解

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <map>
using namespace std;

const int maxn = 1000 + 5;
int p[maxn];
int n;
int tot;
vector<int> vec[maxn];

int find(int x){ return x == p[x] ? x : p[x] = find(p[x]); }
void Union(int x, int y){
x = find(x), y = find(y);
if(x != y){
tot--;
p[x] = y;
}
}

bool common(vector<int>& v1, vector<int>& v2){
for(auto i : v1){
for(auto j : v2){
if(i == j) return true;
}
}
return false;
}

int main(){
#ifndef ONLINE_JUDGE
freopen("data.in", "r", stdin);
#endif // ONLINE_JUDGE

for(int i = 0; i < maxn; ++i) p[i] = i;

cin >> n;
int k, u;
char ch;
for(int i = 0; i < n; ++i){
cin >> k >> ch;
for(int j = 0; j < k; ++j) {
cin >> u;
vec[i].push_back(u);
}
}
tot = n;
for(int i = 0; i < n; ++i){
for(int j = i + 1; j < n; ++j){
if(common(vec[i], vec[j])){
Union(i + 1, j + 1);
}
}
}
// 每个集合的根
vector<int> roots;
for(int i = 1; i <= n; ++i){
if(find(i) == i) roots.push_back(i);
}
cout << tot << endl;

// map 统计每个集合的大小
map<int, int> mp;
for(auto root: roots){
for(int i = 1; i <= n; ++i){
if(find(i) == root) mp[root]++;
}
}
// 用于排序
vector<int> tmp;
for(auto it = mp.begin(); it != mp.end(); ++it){
tmp.push_back(it->second);
}
sort(tmp.begin(), tmp.end(), [](int a, int b){ return a > b;} );
for(int i = 0; i < tmp.size(); ++i){
if(i) cout << " ";
cout << tmp[i];
}
cout << endl;
return 0;
}