Submission #441631

#	Time	Username	Problem	Language	Result	Execution time	Memory
441631		Haruto810198	Love Polygon (BOI18_polygon)	C++17	100 / 100	217 ms	12460 KiB

polygon

#include <bits/stdc++.h>
 
using namespace std;
 
#define int long long
#define double long double
 
#define FOR(i, l, r, d) for(int i=(l); i<=(r); i+=(d))
#define szof(x) ((int)(x).size())
 
#define vi vector<int>
#define pii pair<int,int>
 
#define pb push_back
#define eb emplace_back
#define mkp make_pair
 
const int INF = 2147483647;
const int LNF = INF*INF;
const int MOD = 1000000007;
const int mod = 998244353;
 
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
 
const int MAX = 100010;
 
int n;
map<string, int> mp;
int edge[MAX];
int indeg[MAX];
bool exist[MAX];
 
vi qu;
int res;
 
int query(string str){
    if(mp.find(str) == mp.end()){
        mp[str] = szof(mp) + 1;
    }
    return mp[str];
}
 
signed main(){
 
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
 
    cin>>n;
    FOR(i, 1, n, 1){
        string su, sv;
        cin>>su>>sv;
        int u = query(su);
        int v = query(sv);
        edge[u] = v;
        indeg[v]++;
    }
 
    if(n%2 == 1){
        cout<<-1<<'\n';
        return 0;
    }
 
    FOR(i, 1, n, 1){
        exist[i] = 1;
        if(indeg[i] == 0){
            qu.pb(i);
        }
    }
 
    res = n;
 
    FOR(i, 1, n, 1){
 
        if(exist[i]==0) continue;
 
        if(edge[edge[i]] == i and edge[i] != i){
            res -= 2;
            exist[i] = 0;
            exist[edge[i]] = 0;
            indeg[i]--;
            indeg[edge[i]]--;
        }
 
    }
 
    while(!qu.empty()){
 
        int u = qu.back();
        qu.pop_back();
        if(exist[u]==0) continue;
 
        int v = edge[u];
        if(exist[v]==0) continue;
        int w = edge[v];
 
        exist[u] = 0;
        exist[v] = 0;
        indeg[v]--;
        indeg[w]--;
        res--;
 
        if(indeg[w] == 0 and exist[w] == 1) qu.pb(w);
 
    }
 
    FOR(i, 1, n, 1){
 
        if(exist[i]==0) continue;
 
        int ptr = i;
        int cnt = 0;
        while(exist[ptr] == 1){
            exist[ptr] = 0;
            ptr = edge[ptr];
            cnt++;
        }
 
        if(ptr == i){
            if(cnt == 2){
                res -= 2;
            }
            else{
                res -= cnt / 2;
            }
        }
 
    }
 
    cout<<res<<'\n';
 
    /*
    FOR(i, 1, n, 1){
        cerr<<exist[i]<<" ";
    }
    cerr<<endl;
    */
 
    return 0;
 
}

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