Submission #1091369

#	Time	Username	Problem	Language	Result	Execution time	Memory
1091369		MateiKing80	Love Polygon (BOI18_polygon)	C++14	100 / 100	156 ms	11928 KiB

polygon

#include <bits/stdc++.h>

using namespace std;

int p[100025], n, grad[100025];
map<string, int> nume;
bool vis[100025];
queue<int> q;

int main ()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cin >> n;
    for(int i = 0; i < n; i ++)
    {
        string s, t;
        cin >> s >> t;
        if(!nume.count(s))
            nume[s] = (int)nume.size();
        if(!nume.count(t))
            nume[t] = (int)nume.size();
        p[nume[s]] = nume[t];
        grad[nume[t]] ++;
    }
    if(n % 2 == 1)
    {
        cout << -1;
        return 0;
    }
    int ans = 0;
    for(int i = 0; i < n; i ++)
        if (grad[i] == 0)
            q.push(i);
    while (!q.empty())
    {
        auto k = q.front();
        q.pop();
        if(grad[k] != 0)
            continue;
        if(p[p[k]] != p[k] && p[p[p[k]]] == p[k])
            continue;
        if(p[p[k]] == p[k])
        {
            p[p[k]] = k;
            grad[k] ++;
            grad[p[k]] --;
            ans ++;
            continue;
        }
        ans ++;
        grad[p[p[k]]] --;
        if(grad[p[p[k]]] == 0)
            q.push(p[p[k]]);
        p[p[k]] = k;
        grad[k] ++;
    }
    for(int i = 0; i < n; i ++)
        if(grad[i] == 0)
        {
            ans++;
            grad[i] = 2;
            grad[p[i]] --;
        }
    for(int i = 0; i < n; i ++)
        if(grad[i] == 1 && !vis[i])
        {
            vector<int> t = {i};
            vis[i] = 1;
            int u = p[i];
            while(u != i)
            {
                t.push_back(u);
                vis[u] = 1;
                u = p[u];
            }
            if(t.size() == 2)
                continue;
            int z = t.size();
            ans += (z + 1) / 2;
        }
    cout << ans;
}

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