Submission #382238

#	Time	Username	Problem	Language	Result	Execution time	Memory
382238		pure_mem	Hard route (IZhO17_road)	C++14	0 / 100	10 ms	12160 KiB

road

#include <iostream>
#include <vector>

#define X first
#define Y second
#define MP make_pair
#define ll long long

using namespace std;

const int N = 5e5 + 12;
const int INF = 2e9;

int n, m;
ll ans, mx_ans;
pair<int, int> dp[N];
vector< int > g[N];

void dfs(int v, int pr){
	for(int to: g[v]){
		if(to != pr){
			dfs(to, v);
			if(dp[v].X < dp[to].X + 1){
				dp[v] = dp[to], dp[v].X++;
			}
			else if(dp[v].X == dp[to].X + 1){
				dp[v].Y += dp[to].Y;
			}
		}
	}
	if(g[v].size() == 1 && pr != -1)
		dp[v] = MP(0, 1);	
}
void rdfs(int v, int pr, pair<int, int> mx){
	pair<int, int> mx1 = mx, mx2 = MP(0, 0), mx3 = MP(0, 0);
	int f1 = pr, f2 = 0, f3 = 0;
	for(int to: g[v]){
		if(to != pr){
			pair<int, int> tmp = MP(dp[to].X + 1, dp[to].Y);
			if(mx1 < tmp)
				mx3 = mx2, mx2 = mx1, mx1 = tmp, f3 = f2, f2 = f1, f1 = to;
			else if(mx2 < tmp)
				mx3 = mx2, mx2 = tmp, f3 = f2, f2 = to;
			else if(mx3 < tmp)
				mx3 = tmp, f3 = to;
		}
	}
	if(mx3.X > 0){
		ll tmp = mx1.X * 1ll * (mx2.X + mx3.X);
		if(tmp > mx_ans){
			mx_ans = tmp;
			if(mx1.X == mx2.X && mx2.X == mx3.X)
				ans = 3 * mx1.Y * 1ll * mx2.Y * mx3.Y;
			else if(mx1.X == mx2.X)
				ans = (mx1.Y + mx2.Y) * 1ll * mx3.Y;
			else if(mx1.X == mx3.X)
				ans = (mx1.Y + mx3.Y) * 1ll * mx2.Y;
			else
				ans = mx2.Y * 1ll * mx3.Y;	
		}
		else if(tmp == mx_ans){
			if(mx1.X == mx2.X && mx2.X == mx3.X)
				ans += 3 * mx1.Y * 1ll * mx2.Y * mx3.Y;
			else if(mx1.X == mx2.X)
				ans += (mx1.Y + mx2.Y) * 1ll * mx3.Y;
			else if(mx1.X == mx3.X)
				ans += (mx1.Y + mx3.Y) * 1ll * mx2.Y;
			else
				ans += mx2.Y * 1ll * mx3.Y;
		}
	}
	if(pr == -1 && g[v].size() == 1){
		mx2 = MP(0, 1);	
	} mx1.X += 1, mx2.X += 1, mx3.X += 1;
	for(int to: g[v]){
		if(to != pr){
			if(to != f1){
				rdfs(to, v, mx1);	
			}	
			else if(to != f2){
				rdfs(to, v, mx2);
			}
			else{
				rdfs(to, v, mx3);
			}
		}
	}
}

int main () {
	ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
	cin >> n;
	for(int i = 1, x, y;i < n;i++){
		cin >> x >> y;
		g[x].push_back(y);
		g[y].push_back(x);
	}
	dfs(1, -1);
	rdfs(1, -1, MP(0, 0));
	if(!mx_ans)
		ans = 1;
	cout << mx_ans << " " << ans;
}

Compilation message (stderr)

road.cpp: In function 'void rdfs(int, int, std::pair<int, int>)':
road.cpp:36:23: warning: variable 'f3' set but not used [-Wunused-but-set-variable]
   36 |  int f1 = pr, f2 = 0, f3 = 0;
      |                       ^~

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