Submission #935808

#	Time	Username	Problem	Language	Result	Execution time	Memory
935808		BF001	Hard route (IZhO17_road)	C++17	100 / 100	643 ms	104948 KiB

road

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

#define N 500005
#define int long long
#define fi first
#define se second
typedef pair<int, int> ii;

int n, dp[N], cnt[N], res = 0, way = 1;
vector<int> adj[N];

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;
		//cout << u << ' ' << " " << cur << " " << way << "\n";
	}
	ii f = {0, 1}, s = {0, 0};
	for (auto x : adj[u]){
		if (dp[x] + 1 > f.fi) s = f, f = {dp[x] + 1, cnt[x]};
		else if (dp[x] + 1 == f.fi) f.se += cnt[x];
		else if (dp[x] + 1 > s.fi) s = {dp[x] + 1, cnt[x]};
		else if (dp[x] + 1 == s.fi) s.se += cnt[x];
	}
	int tmpdp = dp[u], tmpcnt = cnt[u];
	for (auto x : adj[u]){
		if (x == p) continue;
		dp[u] = f.fi, cnt[u] = f.se;
		if (dp[x] + 1 == f.fi && cnt[x] == f.se) dp[u] = s.fi, cnt[u] = s.se;
		else if (dp[x] + 1 == f.fi && cnt[x] != f.se) dp[u] = f.fi, cnt[u] = f.se - 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 - 1; 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;

    return 0;
}     

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