Submission #1002577

#	Time	Username	Problem	Language	Result	Execution time	Memory
1002577		BF001	Hard route (IZhO17_road)	C++17	100 / 100	368 ms	105044 KiB

road

#include <bits/stdc++.h>
using namespace std;

#define int long long
#define N 500005
#define fi first
#define se second

typedef pair<int, int> ii;

int ma[N], cnt[N], n, res, way = 1;
vector<int> adj[N];

void dfs(int u, int p){
	cnt[u] = 1;
	for (auto x : adj[u]){
		if (x == p) continue;
		dfs(x, u);
		if (ma[x] + 1 == ma[u]){
			cnt[u] += cnt[x];
		}
		else if (ma[x] + 1 > ma[u]){
			ma[u] = ma[x] + 1;
			cnt[u] = cnt[x];
		}
	}
}

bool cmp(int& a, int& b){
	return ma[a] > ma[b];
}

void rr(int u, int p){
	sort(adj[u].begin(), adj[u].end(), cmp);
	if (adj[u].size() >= 3){
		int a = ma[adj[u][0]] + 1, b = ma[adj[u][1]] + 1, c = ma[adj[u][2]] + 1;
		int m = a * (b + c);
		int w = 0;
		int db = 0;
		a--, b--, c--;
		for (auto x : adj[u]){
			if (ma[x] == c) w += cnt[x] * db;
			if (ma[x] == b) db += cnt[x]; 
		}
		if (m > res) res = m, way = w;
		else if (m == res) way += w;
	}
	ii fir = {0, 1}, sed = {0, 1};
	int tma = ma[u], tmw = cnt[u];
	for (auto x : adj[u]){
		if (ma[x]  + 1> fir.fi){
			sed = fir;
			fir = {ma[x] + 1, cnt[x]};
		}
		else if (ma[x] + 1 == fir.fi) fir.se += cnt[x];
		else if (ma[x] + 1 > sed.fi){
			sed = {ma[x] + 1, cnt[x]};
		}
		else if (ma[x] + 1 == sed.fi) sed.se += cnt[x];
	}
	for (auto x : adj[u]){
		if (x == p) continue;
		ma[u] = fir.fi, cnt[u] = fir.se;
		if (fir.fi == ma[x] + 1 && fir.se == cnt[x]) ma[u] = sed.fi , cnt[u] = sed.se;
		else if (fir.fi == ma[x] + 1) cnt[u] -= cnt[x];
		rr(x, u);
	}
	ma[u] = tma, cnt[u] = tmw;
}

signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);
      
    cin >> n;
    for (int i = 1; i <= n - 1; i++){
    	int u, v;
    	cin >> u >> v;
    	adj[u].push_back(v);
    	adj[v].push_back(u);
    }

    dfs(1, 0);
    rr(1, 0);

    cout << res << " " << way;

    return 0;
}     

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