Submission #727153

#	Time	Username	Problem	Language	Result	Execution time	Memory
727153		ono_de206	Beads and wires (APIO14_beads)	C++14	0 / 100	8 ms	10004 KiB

beads

#include<bits/stdc++.h>
using namespace std;
 
#define fast ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define in insert
#define all(x) x.begin(),x.end()
#define pb push_back
#define eb emplace_back
#define ff first
#define ss second
 
#define int long long
 
typedef long long ll;
typedef vector<int> vi;
typedef set<int> si;
typedef multiset<int> msi;
typedef pair<int, int> pii;
typedef vector<pii> vpii;
 
template<typename T, typename U>
ostream & operator << (ostream &out, const pair<T, U> &c) {
	out << c.first << ' ' << c.second;
    return out;
}
 
template<typename T>
ostream & operator << (ostream &out, vector<T> &v) {
	const int sz = v.size();
	for (int i = 0; i < sz; i++) {
		if (i) out << ' ';
		out << v[i];
	}
    return out;
}
 
template<typename T>
istream & operator >> (istream &in, vector<T> &v) {
	for (T &x : v) in >> x;
    return in;
}
 
 
template<typename T>
void mxx(T &a, T b){if(b > a) a = b;}
template<typename T>
void mnn(T &a, T b){if(b < a) a = b;}
 
const int mxn = 2e5 + 10, inf = 1e18;
int n, f[mxn], g[mxn];
vector<pair<int, int>> adj[mxn];
 
void dfs1(int to, int fr) {
	f[to] = 0;
	g[to] = -inf;
	int mx1 = -inf;
	for(auto it : adj[to]) {
		if(it.ff == fr) continue;
		int x = it.ff;
		dfs1(x, to);
		f[to] += max(f[x], g[x] + it.ss);
		mxx(mx1, f[x] + it.ss - max(f[x], g[x] + it.ss));
	}
	mxx(g[to], f[to] + mx1);
}
 
int ans;
 
void dfs2(int to, int fr, int mx1, int mx2, int d) {
	vector<int> v;
	int tmp = 0;
	if(to != 1) {
		tmp += max(mx1, mx2 + d);
		v.pb(mx1 + d - max(mx1, mx2 + d));
	}
	for(auto it : adj[to]) {
		if(it.ff == fr) continue;
		int x = it.ff;
		tmp += max(f[x], g[x] + it.ss);
		v.pb(f[x] + it.ss - max(f[x], g[x] + it.ss));
	}
	mxx(ans, tmp);
	sort(all(v));
	reverse(all(v));
	if(v.size() > 1) {
		mxx(ans, tmp + v[0] + v[1]);
	}
	int nx1 = 0;
	multiset<int> s;
	if(to != 1) {
		nx1 += mx2 + d;
		s.in(mx1 + d - mx2 - d);
	}
	for(auto it : adj[to]) {
		if(it.ff == fr) continue;
		int x = it.ff;
		nx1 += max(f[x], g[x] + it.ss);
		s.in(f[x] + it.ss - max(f[x], g[x] + it.ss));
	}
	for(auto it : adj[to]) {
		if(it.ff == fr) continue;
		int x = it.ff;
		s.erase(s.find(f[x] + it.ss - max(f[x], g[x] + it.ss)));
		nx1 -= max(f[x], g[x] + it.ss);
		dfs2(x, to, nx1, nx1 + (*s.rbegin()), it.ss);
		s.in(f[x] + it.ss - max(f[x], g[x] + it.ss));
		nx1 += max(f[x], g[x] + it.ss);
	}
}
 
void go() {
	cin >> n;
	for(int i = 1; i < n; i++) {
		int x, y, c;
		cin >> x >> y >> c;
		adj[x].eb(y, c);
		adj[y].eb(x, c);
	}
	dfs1(1, 0);
	dfs2(1, 0, 0, 0, 0);
	cout << ans << '\n';
}
 
signed main() {
	//#ifndef ONO
	//freopen("beads.in", "r", stdin);
	//freopen("beads.out", "w", stdout);
	//#endif
	fast;
	int t = 1;
	// cin >> t;
	while(t--) {
		go();
	}
	return 0;
}

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