Submission #560256

#	Time	Username	Problem	Language	Result	Execution time	Memory
560256		hhhhaura	Beads and wires (APIO14_beads)	C++14	100 / 100	195 ms	29800 KiB

beads

#define wiwihorz
#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC target("sse")
#pragma loop-opt(on)
#define rep(i, a, b) for(int i = a; i <= b; i ++)
#define rrep(i, a, b) for(int i = b; i >= a; i --)
#define all(x) x.begin(), x.end()
#define ceil(a, b) ((a + b - 1) / (b))
#define int long long int
#define lld long double
#define pii pair<int, int>
#define random mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count())
#define INF 1000000000000000000
#define MOD 1000000007
#define eps (1e-9)
using namespace std;
#ifdef wiwihorz
#define print(a...)cerr<<"Line "<<__LINE__<<":",kout("["+string(#a)+"] = ", a)
void vprint(auto L,auto R){while(L<R)cerr<<*L<<" \n"[next(L) == R], ++L; }
void kout() { cerr << endl; }
template<class T1,class ... T2>void kout(T1 a,T2 ... e){cerr<<a<<" ",kout(e...);}
#else
#define print(...) 0
#define vprint(...) 0
#endif
#define x first
#define y second
namespace solver {
	int n, ans = 0;
	vector<int> leaf, dp1, dp2;
	vector<vector<pii>> mp;
	void init_(int _n) {
		n = _n, ans = 0;
		mp.assign(n + 1, vector<pii>());
		dp1.assign(n + 1, 0);
		dp2.assign(n + 1, 0);
		leaf.assign(n + 1, 1);
	}
	void dfs(int x, int par) {
		int v = -INF, sum = 0;
		for(auto i : mp[x]) if(i.x != par) {
			dfs(i.x, x);
			leaf[x] = 0;
			if(leaf[i.x]) v = max(v, i.y);
			else {
				int val = max(dp1[i.x] + i.y, dp2[i.x]);
				sum += val;
				v = max(v, -val + dp2[i.x] + i.y);
			}
		}
		dp1[x] = sum + v;
		dp2[x] = sum;
	}
	void dfs2(int x, int par, int cost, int v1, int v2) {
		int sum = x == par ? 0 : max(v1 + cost, v2);
		int mx = -sum + v2 + cost, sc = -INF;
		for(auto i : mp[x]) if(i.x != par) {
			if(leaf[i.x]) {
				int tmp = i.y;
				if(tmp > mx) swap(tmp, mx);
				if(tmp > sc) swap(tmp, sc); 
			}
			else {
				int val = max(dp1[i.x] + i.y, dp2[i.x]);
				int tmp = -val + dp2[i.x] + i.y;
				sum += val;
				if(tmp > mx) swap(tmp, mx);
				if(tmp > sc) swap(tmp, sc);
			}
		}
		ans = max(ans, sum);
		for(auto i : mp[x]) if(i.x != par) {
			if(leaf[i.x]) {
				int cur = (mx == i.y ? sc : mx);
				dfs2(i.x, x, i.y, sum + cur, sum);
			}
			else {
				int val = max(dp1[i.x] + i.y, dp2[i.x]);
				int tmp = -val + dp2[i.x] + i.y;
				int cur = (mx == tmp ? sc : mx);
				dfs2(i.x, x, i.y, sum - val + cur, sum - val);
			}
		}
	}
	void solve() {
		int root = 1;
		rep(i, 1, n) if(mp[i].size() != 1) root = i;
		if(mp[root].size() == 1) cout << "0\n";
		else {
			dfs(root, root);
			dfs2(root, root, 0, -INF, -INF);
			ans = max(ans, dp2[root]);
			cout << ans << "\n";
		}
	}

};
using namespace solver;
signed main() {
	ios::sync_with_stdio(false), cin.tie(0);
	int n; cin >> n;
	init_(n);
	rep(i, 1, n - 1) {
		int a, b, c;
		cin >> a >> b >> c;
		mp[a].push_back({b, c});
		mp[b].push_back({a, c});
	}
	solve();
	return 0;
}

Compilation message (stderr)

beads.cpp:5: warning: ignoring '#pragma loop ' [-Wunknown-pragmas]
    5 | #pragma loop-opt(on)
      | 
beads.cpp:20:13: warning: use of 'auto' in parameter declaration only available with '-fconcepts-ts'
   20 | void vprint(auto L,auto R){while(L<R)cerr<<*L<<" \n"[next(L) == R], ++L; }
      |             ^~~~
beads.cpp:20:20: warning: use of 'auto' in parameter declaration only available with '-fconcepts-ts'
   20 | void vprint(auto L,auto R){while(L<R)cerr<<*L<<" \n"[next(L) == R], ++L; }
      |                    ^~~~

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