Submission #1031501

#	Time	Username	Problem	Language	Result	Execution time	Memory
1031501		codexistent	Love Polygon (BOI18_polygon)	C++14	50 / 100	378 ms	33752 KiB

polygon

#include <bits/stdc++.h>
using namespace std;
#define MAXN 100005
#define FOR(i, a, b) for(int i = a; i <= b; i++)
#define f first
#define s second
 
int n, ec[MAXN];
string st[MAXN], nx[MAXN];
map<string, int> idx;
set<int> adj[MAXN];
set<pair<int, int>> se;
bool d[MAXN];
 
int main(){
    cin >> n;
    FOR(i, 1, n) ec[i] = 0;
    FOR(i, 1, n){
        cin >> st[i];
        idx.insert({st[i], i});
        cin >> nx[i];
    }
 
    if(n % 2) {
        cout << -1 << endl;
        return 0;
    }
 
    int r = 0;
    FOR(i, 1, n){
        d[i] = (idx[nx[idx[nx[i]]]] == i && idx[nx[i]] != i);
    }
 
    FOR(i, 1, n){
        if(i == idx[nx[i]] || d[i] || d[idx[nx[i]]]) continue;
        adj[i].insert(idx[nx[i]]);
        adj[idx[nx[i]]].insert(i);
    }
 
    int ct = 0;
    FOR(i, 1, n) if(!d[i]) ct++, se.insert({(int)adj[i].size(), i});
 
    while(ct && se.size()){
        auto si = *se.begin();

        d[si.s] = true, ct--;
 
        if(si.f == 0){
            r++;
        }else{
            int j = 0, jmn = INT_MAX;
            for(int i : adj[si.s]){
                if(jmn > (int)adj[i].size()) j = i, jmn = (int)adj[i].size();
            }
            r++;
 
            se.erase({jmn, j});
            for(int j2 : adj[j]){
                se.erase({(int)adj[j2].size(), j2});
                adj[j2].erase(j);
                se.insert({(int)adj[j2].size(), j2});
            }
        }
 
        for(int i2 : adj[si.s]) {
            se.erase({(int)adj[i2].size(), i2});
            adj[i2].erase(si.s);
            se.insert({(int)adj[i2].size(), i2});
        }
 
        se.erase(se.begin());
    }

 
    cout << r << endl;
}

• Subtask 1: 21 / 21
• Subtask 2: 0 / 25
• Subtask 3: 29 / 29
• Subtask 4: 0 / 25