Submission #972331

#	Time	Username	Problem	Language	Result	Execution time	Memory
972331		pcc	Beads and wires (APIO14_beads)	C++17	0 / 100	2 ms	6520 KiB

beads

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

#define ll long long
#define pll pair<ll,ll>
#define pii pair<int,int>
#define fs first
#define sc second
#define tlll tuple<ll,ll,ll>

const int mxn = 2e5+10;
vector<pii> tree[mxn];
int dp[mxn][2];
int N;
int ans = 0;

void dfs(int now,int par,int up){
	dp[now][0] = dp[now][1] = 0;
	vector<int> v;
	for(auto [nxt,w]:tree[now]){
		if(nxt == par)continue;
		dfs(nxt,now,w);
		dp[now][0] += dp[nxt][1];
		dp[now][1] += dp[nxt][1];
		v.push_back(dp[nxt][0]-dp[nxt][1]+w);
	}
	sort(v.rbegin(),v.rend());
	if(v.empty())dp[now][0] = dp[now][1] = 0;
	else if(v.size() == 1)dp[now][0] = 0,dp[now][1] += v[0]+up;
	else dp[now][0] += v[0]+v[1],dp[now][1] += v[0]+up;
	if(up)ans = max({ans,dp[now][0],dp[now][1]});
	else ans = max(ans,dp[now][0]);
	return;
}

int main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin>>N;
	for(int i = 1;i<N;i++){
		int a,b,c;
		cin>>a>>b>>c;
		tree[a].push_back(pii(b,c));
		tree[b].push_back(pii(a,c));
	}
	dfs(1,1,0);
	cout<<ans<<'\n';
	return 0;
}

• Subtask 1: 0 / 13
• Subtask 2: 0 / 15
• Subtask 3: 0 / 29
• Subtask 4: 0 / 43