Submission #391676

#	Time	Username	Problem	Language	Result	Execution time	Memory
391676		Victor	Love Polygon (BOI18_polygon)	C++17	25 / 100	194 ms	32716 KiB

polygon

#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for (int i = a; i < b; ++i)
#define per(i, a, b) for (int i = b - 1; i >= a; --i)
#define trav(a, x) for (auto& a : x)
#define sz(a) a.size()

typedef pair<int, int> ii;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<vi> vvi;

unordered_map<string, string> people;
unordered_set<string> vis;

int si;
void dfs(string person){
    if(vis.count(person))return;
    vis.insert(person);
    ++si;
    dfs(people[person]);
}

int main() {
    cin.tie(0)->sync_with_stdio(0);

    int n;
    cin >> n;
    if (n & 1) {
        cout << -1 << endl;
        return 0;
    }

    int ans=0;
    string n1, n2;
    rep(i, 0, n) {
        cin >> n1 >> n2;
        people.emplace(n1, n2);

        if (n1!=n2&&people.count(n2) && people[n2] == n1) {
            people.erase(n1);
            people.erase(n2);
        }
    }


    trav(person,people){
        si=0;
        dfs(person.first);
        ans+=(si+1)>>1;
    }
    cout<<ans<<endl;
}

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