Submission #491553

#	Time	Username	Problem	Language	Result	Execution time	Memory
491553		mnair797	Hard route (IZhO17_road)	C++17	100 / 100	786 ms	91308 KiB

road

#include <iostream>
#include <vector>
#include <algorithm>
#include <stack>
#include <queue>
#include <cmath>
#include <iomanip>
#include <unordered_map>
#include <utility>
#include <assert.h>
using namespace std;
void debug() {cout << endl;}
template <class T, class ...U> void debug(T a, U ... b) { cout << a << " "; debug(b...);}
template <class T> void pary(T l, T r) {
	while (l != r) {cout << *l << " ";l++;}
	cout << endl;
}
#define ll long long
#define ld long double
#define maxn 500005
#define mod 1000000007
#define pii pair<int, int>
#define ff first
#define ss second
#define io ios_base::sync_with_stdio(0);cin.tie(0);
vector<int> adj[maxn];
int f[maxn][3], cnt[maxn][2], deg[maxn], up[maxn], down[maxn], g[maxn][3];
void upd(int x, int n, int y) {
	if (x > f[n][0]) {
		f[n][2] = f[n][1], f[n][1] = f[n][0], f[n][0] = x;
		g[n][2] = g[n][1], g[n][1] = g[n][0], g[n][0] = y;
	} else if (x > f[n][1]){
		f[n][2] = f[n][1], f[n][1] = x;
		g[n][2] = g[n][1], g[n][1] = y;
	} else if (x > f[n][2]){
		f[n][2] = x, g[n][2] = y;
	}
}
void dfs(int n, int par) {
	for (int v:adj[n]) {
		if (v != par) {
			dfs(v, n);
			int x = f[v][0] + 1;
			if (x > f[n][0]) cnt[n][0] = cnt[v][0];
			else if (x == f[n][0]) cnt[n][0] += cnt[v][0];
			upd(x, n, cnt[v][0]);
		}
	}
	down[n] = f[n][0];
	if (deg[n] == 1) cnt[n][0]++;
}
void dfs2(int n, int par, int d) {
	upd(d, n, cnt[n][1]);
	up[n] = d;
	int best = d, bcnt = cnt[n][1], sec = 0, scnt = 0;
	for (int v:adj[n]) {
		if (v != par) {
			int x = f[v][0] + 1;
			if (x > best) sec = best, scnt = bcnt, best = x, bcnt = cnt[v][0];
			else if (x == best) bcnt += cnt[v][0];
			else if (x > sec) sec = x, scnt = cnt[v][0];
			else if (x == sec) scnt += cnt[v][0];
		}
	}
	for (int v:adj[n]) {
		if (v != par) {
			if (f[v][0] + 1 == best) {
				if (bcnt > cnt[v][0]) cnt[v][1] = bcnt - cnt[v][0], dfs2(v, n, best + 1);
				else cnt[v][1] = scnt, dfs2(v, n, sec + 1);
			} else {
				cnt[v][1] = bcnt;
				dfs2(v, n, best + 1);
			}
		}
	}
}
ll ans = 0, num = 0;
void solve(int n, int par) {
	vector<int> arr;
	for (int v:adj[n]) {
		if (v != par) {
			if (down[v] + 1	== f[n][2]) arr.push_back(cnt[v][0]);
		}
	}
	if (par && up[n] == f[n][2]) arr.push_back(cnt[n][1]);
	ll tot = 0, nums = 0;
	for (int i:arr) tot += i;
	//debug(n);
	//pary(arr.begin(), arr.end());
	if (f[n][0] && f[n][1] && f[n][2]) {
		if (f[n][0] == f[n][1] && f[n][1] == f[n][2]) {
			ll p1 = 0;
			for (int i:arr) {
				nums += p1 * i;
				p1 += i;
			}
		} else if (f[n][0] == f[n][1]) {
			nums += tot * (g[n][1] + g[n][0]);
		} else if (f[n][1] == f[n][2]) {
			ll p1 = 0;
			for (int i:arr) nums += p1 * i, p1 += i;
		} else {
			nums += tot * g[n][1];
		}
		tot = (ll)f[n][0] * (f[n][1] + f[n][2]);
		//debug(n, tot, nums);
		if (tot > ans) ans = tot, num = nums;
		else if (ans == tot) num += nums;
	}
	for (int v:adj[n]) {
		if (v != par) solve(v, n);
	}
}
int main() {
	io
	int n;
	cin >> n;
	for (int i = 0;i < n - 1;i++) {
		int u, v;
		cin >> u >> v;
		adj[u].push_back(v);
		adj[v].push_back(u);
		deg[u]++, deg[v]++;
	}
	int root = 0;
	for (int i = 1;i <= n;i++) {
		if (deg[i] > 2) {
			root = i;
			break;
		}
	}
	if (!root) {
		cout << 0 << " " << 1 << endl;
		return 0;
	}
	dfs(root, 0);
	dfs2(root, 0, 0);
	//debug(root);
	//for (int i = 1;i <= n;i++) debug(f[i][0], f[i][1], f[i][2]);
	solve(root, 0);
	cout << ans << " " << num << endl;
}

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