Submission #670128

#	Time	Username	Problem	Language	Result	Execution time	Memory
670128		radal	Beads and wires (APIO14_beads)	C++17	0 / 100	3 ms	4948 KiB

beads

#include <bits/stdc++.h>
#pragma GCC target("sse,sse2,avx2")
#pragma GCC optimize("unroll-loops,O2")
#define rep(i,l,r) for (int i = l; i < r; i++)
#define repr(i,r,l) for (int i = r; i >= l; i--)
#define X first
#define Y second
#define all(x) (x).begin() , (x).end()
#define pb push_back
#define endl '\n'
#define debug(x) cerr << #x << " : " << x << endl;
using namespace std;
typedef long long ll;
typedef pair<int,int> pll;
constexpr int N = 2e5+10,mod = 1e9+7,maxm = 210;
constexpr ll inf = 1e9+10;
inline int mkay(int a,int b){
    if (a+b >= mod) return a+b-mod;
   // if (a+b < 0) return a+b+mod;
    return a+b;
}
 
inline int poww(int a,int k){
    if (k < 0) return 0;
    int z = 1;
    while (k){
        if (k&1) z = 1ll*z*a%mod;
        a = 1ll*a*a%mod;
        k >>= 1;
    } 
    return z; 
}
 
vector<pll> adj[N];
int dp[N][2];
int h[N];
 
void pre(int v,int p){
	for (auto [u,w] : adj[v]){
		if (u != p){
			h[u] = h[v]+w;
			pre(u,v);
		}
	}
}

void dfs(int v,int p){
	if ((int) adj[v].size() == 1 && p != 0){
		dp[v][1] = -2*inf;
		dp[v][0] = 0;
		return;
	}
//	vector<int> ve;
	int s = 0,mx = -2*inf;
	for (auto [u,w] : adj[v]){
		if (u == p) continue;
		dfs(u,v);
		int val = max(dp[u][0],dp[u][1]+w);
		s += val;
		mx = max(mx,dp[u][0]-val+w);
//		ve.pb(dp[u][0]-val+w);
 
	}
//	sort(all(ve));
	dp[v][0] = s;
	dp[v][1] = s + mx;
}
 
int main(){
	ios :: sync_with_stdio(0); cin.tie(0); 
	int n;
	cin >> n;
	rep(i,1,n){
		int u,v,w;
		cin >> u >> v >> w;
		adj[u].pb({v,w});
		adj[v].pb({u,w});
	}
	if (n <= 2){
		cout << 0 << endl;
		return 0;
	}
	pre(1,0);
	int vert = 1,mx = 0;
	rep(i,1,n+1){
		if (h[i] > mx){
			mx = h[i];
			vert = i;
		}
	}
	int ans = 0;
	dfs(vert,0);
	ans = max(ans,dp[vert][0]);
/*	rep(i,1,n+1){
		if ((int)adj[i].size() > 1) continue;
	   	dfs(i,0);
		ans = max(ans,dp[i][0]);
	}*/
	cout << ans;
}

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