제출 #538709

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
538709		S2speed	구슬과 끈 (APIO14_beads)	C++17	100 / 100	558 ms	55360 KiB

beads

#include<bits/stdc++.h>

using namespace std;

#define all(x) x.begin() , x.end()
typedef long long ll;
typedef pair<ll , ll> pll;

const ll maxn = 2e5 + 16 , inf = 2e16;

ll dp[maxn][2] , w[maxn];
vector<pll> adj[maxn];
multiset<ll , greater<ll>> s[maxn];

void dDFS(ll r , ll par){
	ll res = 0 , mx;
	s[r].insert(-inf);
	for(auto p : adj[r]){
		ll i = p.first , w = p.second;
		if(i == par) continue;
		dDFS(i , r);
		ll h = max(dp[i][0] , dp[i][1] + w) , o = dp[i][0] + w - h;
		res += h;
		s[r].insert(o);
	}
	dp[r][1] = res + *s[r].begin();
	dp[r][0] = res;
	return;
}

void reroot(ll v , ll u , ll w){
	ll h = max(dp[u][0] , dp[u][1] + w) , o = dp[u][0] + w - h;
	s[v].erase(s[v].find(o));
	dp[v][0] -= h;
	dp[v][1] = dp[v][0] + *s[v].begin();
	h = max(dp[v][0] , dp[v][1] + w); o = dp[v][0] + w - h;
	s[u].insert(o);
	dp[u][0] += h;
	dp[u][1] = dp[u][0] + *s[u].begin();
	return;
}

ll ans = 0;

void rDFS(ll r , ll par){
	ans = max(ans , dp[r][0]);
	for(auto p : adj[r]){
		ll i = p.first , w = p.second;
		if(i == par) continue;
		reroot(r , i , w);
		rDFS(i , r);
		reroot(i , r , w);
	}
	return;
}

int main(){
	ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);

	ll n;
	cin>>n;
	for(ll i = 1 ; i < n ; i++){
		ll v , u , w;
		cin>>v>>u>>w; v--; u--;
		adj[v].push_back({u , w}); adj[u].push_back({v , w});
	}
	dDFS(0 , -1);
	rDFS(0 , -1);
	cout<<ans<<'\n';
	return 0;
}

컴파일 시 표준 에러 (stderr) 메시지

beads.cpp: In function 'void dDFS(ll, ll)':
beads.cpp:16:15: warning: unused variable 'mx' [-Wunused-variable]
   16 |  ll res = 0 , mx;
      |               ^~

• Subtask 1: 13 / 13
• Subtask 2: 15 / 15
• Subtask 3: 29 / 29
• Subtask 4: 43 / 43