Submission #1105857

#	Time	Username	Problem	Language	Result	Execution time	Memory
1105857		koukirocks	Love Polygon (BOI18_polygon)	C++17	54 / 100	115 ms	19204 KiB

polygon

#include <bits/stdc++.h>
#define speed ios_base::sync_with_stdio(0); cin.tie(0)
#define all(x) (x).begin(),(x).end()
#define F first
#define S second
//#pragma GCC optimize("O3,unroll-loops")
//#pragma GCC target("avx,avx2")
//#pragma GCC target("popcnt")
 
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ldb;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
 
const ll MAX=2e5+10,P=1e9+7;
const ll INF=0x3f3f3f3f,oo=0x3f3f3f3f3f3f3f3f;
const ldb eps=1e-6;
const ldb PI=acos(-1.0);
const int dir[4][2]={{0,1},{0,-1},{1,0},{-1,0}};
template<typename T>
using vvector = vector<vector<T>>;

int main() {
    speed;
    int n;
    vector<pair<string,string>> e;
    vector<string> d;
    cin>>n;
    for (int i=0;i<n;i++) {
        string a,b;
        cin>>a>>b;
        e.emplace_back(a,b);
        d.push_back(a);
        d.push_back(b);
    }
    if (n&1) {
        cout<<"-1\n";
        return 0;
    }
    sort(all(d));
    d.resize(unique(all(d))-d.begin());
    n=d.size();
    vector<int> G(n+1);
    vector<int> ind(n+1),vis(n+1);
    int ans=0;
    for (int i=0;i<n;i++) {
        int a=lower_bound(all(d),e[i].F)-d.begin()+1,b=lower_bound(all(d),e[i].S)-d.begin()+1;
        // if (a==b) G[a]=0;
        // else {
            G[a]=b;
            ind[b]++;
        // }
    }
    queue<int> q;
    for (int i=1;i<=n;i++) {
        if (ind[i]==0) q.push(i);
    }
    while (!q.empty()) {
        int v=q.front();
        q.pop();
        ans++;
        if (!vis[G[v]]) {
            // cout<<v<<" "<<G[v]<<" v gv\n";
            vis[G[v]]=true;
            ind[G[G[v]]]--;
            if (ind[G[G[v]]]==0 and !vis[G[G[v]]]) q.push(G[G[v]]);
        }
        // cout<<v<<" v\n";
        vis[v]=true;
    }
    for (int i=1;i<=n;i++) {
        if (vis[i]) continue;
        int now=i;
        int sz=0;
        while (!vis[now]) {
            vis[now]=true;
            sz++;
            now=G[now];
        }
        if (sz==1) ans++;
        else if (sz!=2) {
            ans+=(sz/2)+(sz&1);
        }
    }
    cout<<ans<<"\n";
    return 0;
}

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