Submission #610538

#	Time	Username	Problem	Language	Result	Execution time	Memory
610538		Arnch	Mousetrap (CEOI17_mousetrap)	C++17	25 / 100	899 ms	79684 KiB

mousetrap

// oooo
/*
 har chi delet mikhad bebar ~
 gitar o ba khodet nabar! ~
 ;Amoo_Hasan;
*/

#include<bits/stdc++.h>
//#pragma GCC optimize("O3,no-stack-protector,unroll-loops")
//#pragma GCC target("avx2,fma")

using namespace std;

typedef long long ll;
typedef long double ld;

#define Sz(x) int((x).size())
#define All(x) (x).begin(), (x).end()
#define wtf(x) cout<<#x <<" : " <<x <<endl

constexpr ll inf = 1e18, N = 1e6 + 10, mod = 1e9 + 7, pr = 1000696969;

int n, t, m;
bool mark[N];
ll dp[N], par[N], ps[N];
vector<int> adj[N];

void dfs(int x, int p = 0) {
	par[x] = p;

	int tim = 0;
	vector<ll> vc;
	for(auto j : adj[x]) {
		if(j == p) continue;
		tim++;
		dfs(j, x);
		vc.push_back(dp[j]);
	}

	sort(All(vc), greater<int>());

	if(x != t) {
		ps[x] = ps[p] + tim - 1;
	}
	
	if(tim == 0) {
		dp[x] = 0;
		return;
	}
	if(tim == 1) {
		dp[x] = 1;
		return;
	}

	dp[x] = tim;
	dp[x] += vc[1];
}

ll solve(int x) {
	vector<ll> vc;
	for(auto j : adj[x]) {
		if(mark[j] || j == par[x]) continue;
		vc.push_back(dp[j]);
	}
	sort(All(vc), greater<int>());

	ll cnt = ps[par[x]];
	cnt += Sz(vc);

	if(Sz(vc) >= 2) cnt += vc[1];

	return cnt;
}


int main() {
    ios :: sync_with_stdio(0), cin.tie(0);

	cin >>n >>t >>m;
	for(int i = 0; i < n - 1; i++) {
		int u, v; cin >>u >>v;
		adj[u].push_back(v), adj[v].push_back(u);
	}

	dfs(t);

	ll ans = solve(m);

	mark[m] = 1;
	
	int x = par[m];
 
	while(x != t) {
		ans = max(ans, solve(x));

		mark[x] = 1;
		x = par[x];
	}
 
	cout<<ans;
 
	

    return 0;
}

• Subtask 1: 0 / 20
• Subtask 2: 25 / 25
• Subtask 3: 0 / 20
• Subtask 4: 0 / 35