Submission #1105835

#	Time	Username	Problem	Language	Result	Execution time	Memory
1105835		koukirocks	Love Polygon (BOI18_polygon)	C++17	25 / 100	108 ms	21032 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;
        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();
        if (vis[v]) ans++;
        else if (vis[G[v]]) ans++;
        else vis[G[v]]=true;
        vis[v]=true;
        if (--ind[G[v]]==0) q.push(G[v]);
    }
    for (int i=1;i<=n;i++) {
        if (vis[i]) continue;
        vector<int> ccl;
        ccl.push_back(i);
        int now=G[i];
        while (now!=ccl[0]) {
            ccl.push_back(now);
            now=G[now];
        }
        for (int i:ccl) vis[i]=true;
        if (ccl.size()!=2) {
            ans+=(ccl.size()/2)+(ccl.size()&1);
        }
    }
    cout<<ans<<"\n";
    return 0;
}

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