Submission #311492

#	Time	Username	Problem	Language	Result	Execution time	Memory
311492		OttoTheDino	Love Polygon (BOI18_polygon)	C++17	100 / 100	299 ms	11576 KiB

polygon

#include <bits/stdc++.h>
using namespace std;

#define rep(n)      for (int i = 0; i < n; ++i)
#define rep2(n)     for (int j = 0; j < n; ++j)
#define mp          make_pair
#define pb          push_back
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> ii;

const int maxn = 2e5;

int loves[maxn];
bool been[maxn] = {};

int dfs (int i) {
    been[i] = 1;
    return 1+(been[loves[i]]?0:dfs(loves[i]));
}

int main() {    
    ios::sync_with_stdio(0);
    cin.tie(0);
    
    map<string, int> decode;
    int n, num = 1, loved[maxn], ans = 0;
    string s, t;
    cin >> n;
    
    rep (n) {
        cin >> s >> t;
        if (!decode[s]) decode[s] = num++;
        if (!decode[t]) decode[t] = num++;
        loves[decode[s]] = decode[t];
        loved[decode[t]]++;
    }
    
    if (n%2==1) {
        cout << "-1\n";
        return 0;
    }
    
    queue<int> q;
    
    for (int i = 1; i <= n; ++i) {
        if (i==loves[loves[i]] && loves[i]!=i) {
            been[i] = 1;
            been[loves[i]] = 1;
        }
        else if (loved[i]==0) q.push(i);
    }
    
    while (!q.empty()) {
        int id = q.front();
        q.pop();
        been[id] = 1;
        if (!been[loves[id]]) {
            been[loves[id]] = 1;
            if (--loved[loves[loves[id]]]==0) q.push(loves[loves[id]]);
        }
        ans++;
    }
    
    for (int i = 1; i <= n; ++i) {
        if (!been[i]) ans += (dfs(i)+1)/2;
    }
    
    cout << ans << "\n";
    
    return 0;
}

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