Submission #947636

#	Time	Username	Problem	Language	Result	Execution time	Memory
947636		atom	Hard route (IZhO17_road)	C++17	52 / 100	565 ms	1364 KiB

road

#include "bits/stdc++.h"
// @JASPER'S BOILERPLATE
using namespace std;
using ll = long long;

#ifdef JASPER
#include "debug.h"
#else
#define debug(...) 166
#endif

const int N = 5e3 + 5;
const int INF = 1e9;
int n;
vector <int> adj[N];
ll ans, cnt;
using T = pair <ll, ll>;

T dp[N];
// <maximum distance from current node, number of ways>
void dfs(int u, int p, int dep) {
    dp[u] = make_pair(dep, 1);
    for (int v : adj[u]) {
        if (v == p) continue;
        dfs(v, u, dep + 1);
        if (dp[u].first < dp[v].first)
            dp[u] = make_pair(dp[v].first, dp[v].second);
        else if (dp[u].first == dp[v].first)
            dp[u].second += dp[v].second;
    }
}

signed main() {
    cin.tie(0) -> sync_with_stdio(0);

    cin >> n;
    for (int i = 1; i < n; ++i) {
        int u, v; cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    //sub2: O(n^2)
    ans = 0, cnt = 1;
    for (int u = 1; u <= n; ++u) {
        dfs(u, u, 0);

        vector <T> cand;
        for (int v : adj[u]) cand.push_back(dp[v]);
        sort(cand.rbegin(), cand.rend());
        debug(cand);
        if ((int) cand.size() <= 2) continue; // at least three candidates;

        ll hardness = cand[0].first * (cand[1].first + cand[2].first);
        ll cur_cnt = 0;
        ll d = 0;
        for (int i = 0; i < (int) (cand.size()); ++i) {
            if (cand[i].first == cand[2].first) cur_cnt += d * cand[2].second;
            if (cand[i].first == cand[1].first) d += cand[i].second;
            
        }
        if (ans < hardness) {
            ans = hardness;
            cnt = cur_cnt;
        }
        else if (ans == hardness)
            cnt += cur_cnt;
    }

    cout << ans << " " << cnt << "\n";

    return 0;
}

/*
    leaf nodes always product maximum distance?
*/

Compilation message (stderr)

road.cpp: In function 'int main()':
road.cpp:9:20: warning: statement has no effect [-Wunused-value]
    9 | #define debug(...) 166
      |                    ^~~
road.cpp:51:9: note: in expansion of macro 'debug'
   51 |         debug(cand);
      |         ^~~~~

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