Submission #172251

#	Time	Username	Problem	Language	Result	Execution time	Memory
172251		emil_physmath	Hard route (IZhO17_road)	C++17	0 / 100	12 ms	12152 KiB

road

#include <algorithm>
#include <vector>
#include <iostream>
#include <map>
using namespace std;
typedef long long llong;
const int maxN = 500005;

vector<int> nei[maxN];
pair<int, int> ray[maxN][3];

inline ostream& operator<<(ostream& ostr, const pair<int, int>& a)
{
    return ostr << "{" << a.first << ", " << a.second << "}";
}
inline const pair<int, int>& Second(const pair<int, int>* a)
{
    return a[0].second >= 2 ? a[0] : a[1];
}
void Maximize(pair<int, int>* a, pair<int, int> x)
{
    if (a[0].first == x.first)
        a[0].second += x.second;
    else if (a[1].first == x.first)
        a[1].second += x.second;
    else if (a[2].first == x.first)
        a[2].second += x.second;
    else if (x.first > a[2].first)
    {
        a[2] = x;
        sort(a, a + 3, greater<pair<int, int>>());
    }
}
void SetDown(int v, int par)
{
    fill(ray[v], ray[v] + 3, make_pair(0, 0));
    ray[v][0] = {0, 1};
    for (int to: nei[v])
        if (to != par)
        {
            SetDown(to, v);
            Maximize(ray[v], {ray[to][0].first + 1, 1});
        }
}
void SetUp(int v, int par)
{
    for (int to: nei[v])
        if (to != par)
        {
            // Set up[to].
            if (ray[v][0].first == ray[to][0].first + 1)
                Maximize(ray[to], {Second(ray[v]).first + 1, 1});
            else
                Maximize(ray[to], {ray[v][0].first + 1, 1});
            SetUp(to, v);
        }
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    int n;
    cin >> n;
    for (int i = 1; i < n; ++i)
    {
        int u, v;
        cin >> u >> v;
        nei[u].push_back(v);
        nei[v].push_back(u);
    }
    SetDown(1, -1);
    /*for (int v = 1; v <= n; ++v)
        cerr << v << ": " << ray[v][0] << ' ' << ray[v][1] << ' ' << ray[v][2] << endl;*/
    SetUp(n - rand() % n, -1);
    map<llong, llong> ans;
    for (int v = 1; v <= n; ++v)
    {
        // cerr << v << ": " << ray[v][0] << ' ' << ray[v][1] << ' ' << ray[v][2] << endl;
        vector<pair<llong, int>> x;
        for (int i = 0; i < 3; ++i)
            if (ray[v][i].first)
            {
                for (int j = 0; j < min(3, ray[v][i].second); ++j)
                    x.push_back({ray[v][i].first, min(3, ray[v][i].second)});
            }
        if (x.size() < 3) continue;
        int cnt = 0;
        if (x[1].first == x[2].first)
            cnt = (x[1].second * (x[1].second - 1LL)) / 2LL;
        else
            cnt = x[1].second * (llong)x[2].second;
        ans[x[0].first * (x[1].first + x[2].first)] += cnt;
    }
    /*for (auto it: ans)
        cerr << it.first << ' ' << it.second << endl;*/
    if (ans.size())
        cout << ans.rbegin()->first << ' ' << ans.rbegin()->second;
    else
        cout << "0 1";
}

• Subtask 1: 0 / 19
• Subtask 2: 0 / 33
• Subtask 3: 0 / 48