Submission #960815

#	Time	Username	Problem	Language	Result	Execution time	Memory
960815		Trisanu_Das	Hard route (IZhO17_road)	C++17	100 / 100	578 ms	105056 KiB

road

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ff first
#define ss second
 
int n, dp[500005], cnt[500005], res = 0, way = 1;
vector<int> adj[500005];
 
void init(int u, int p){
	cnt[u] = 1;
	for (auto x : adj[u]){
		if (x == p) continue;
		init(x, u);
		if (dp[x] + 1 == dp[u]) cnt[u] += cnt[x];
		if (dp[x] + 1 > dp[u]) cnt[u] = cnt[x];
		dp[u] = max(dp[u], dp[x] + 1);
	}
}
 
bool cmp (int& i, int& j){
	return dp[i] > dp[j];
}
 
void rr(int u, int p){
	sort(adj[u].begin(), adj[u].end(), cmp);
	if (adj[u].size() >= 3){
		int cur = 0, cn = 0;
		int a = dp[adj[u][0]] + 1, b = dp[adj[u][1]] + 1, c = dp[adj[u][2]] + 1;
		cur = a * (b + c);
		int ca = 0;
		for (auto x : adj[u]){
			if (dp[x] + 1 == c) cn += ca * cnt[x];
			if (dp[x] + 1 == b) ca += cnt[x];
		}
		if (cur > res) res = cur, way = cn;
		else if (cur == res) way += cn;
	}
	pair<int, int> f = {0, 1}, s = {0, 0};
	for (auto x : adj[u]){
		if (dp[x] + 1 > f.ff) s = f, f = {dp[x] + 1, cnt[x]};
		else if (dp[x] + 1 == f.ff) f.ss += cnt[x];
		else if (dp[x] + 1 > s.ff) s = {dp[x] + 1, cnt[x]};
		else if (dp[x] + 1 == s.ff) s.ss += cnt[x];
	}
	int tmpdp = dp[u], tmpcnt = cnt[u];
	for (auto x : adj[u]){
		if (x == p) continue;
		dp[u] = f.ff, cnt[u] = f.ss;
		if (dp[x] + 1 == f.ff && cnt[x] == f.ss) dp[u] = s.ff, cnt[u] = s.ss;
		else if (dp[x] + 1 == f.ff && cnt[x] != f.ss) dp[u] = f.ff, cnt[u] = f.ss - cnt[x];
		rr(x, u);
	}
	dp[u] = tmpdp, cnt[u] = tmpcnt;
}
 
signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(NULL); 
    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);
    }
    init(1, 0);
    rr(1, 0);
    cout << res << ' ' << way;
}

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