Submission #853654

#	Time	Username	Problem	Language	Result	Execution time	Memory
853654		NK_	Tug of War (BOI15_tug)	C++17	0 / 100	151 ms	2488 KiB

tug

// Success consists of going from failure to failure without loss of enthusiasm
#include <bits/stdc++.h>
 
using namespace std;
 
#define nl '\n'
#define pb push_back
#define pf push_front
 
#define mp make_pair
#define f first
#define s second
#define sz(x) int(x.size())
 
template<class T> using V = vector<T>;
using pi = pair<int, int>;
using vi = V<int>;
using vpi = V<pi>;
 
using ll = long long;
using pl = pair<ll, ll>;
using vpl = V<pl>;
using vl = V<ll>;
 
using db = long double;
 
template<class T> using pq = priority_queue<T, V<T>, greater<T>>;
 
const int MOD = 1e9 + 7;
const ll INFL = ll(1e17);
const int LG = 18;

const int nax = 3e4 + 5;
const int kax = 20;
using B = bitset<nax * kax>;
 
int main() {
	cin.tie(0)->sync_with_stdio(0);
 
	int N, K; cin >> N >> K;
	int M = N; N += N;

	vi deg(N); vi W(N);
	V<vpi> adj(N); for(int i = 0; i < N; i++) {
		int u, v, w; cin >> u >> v >> w; --u, --v, v += M;
		W[i] = w;
		adj[u].pb(mp(v, i));
		adj[v].pb(mp(u, i));
		deg[u]++, deg[v]++;
	}

	queue<int> q; for(int i = 0; i < N; i++) {
		if (deg[i] == 1) q.push(i);
	}

	vi used(N), vis(N); int BAL = 0;
	while(sz(q)) {
		int u = q.front(); q.pop();

		vis[u] = 1;

		int x = 0;
		for(auto& e : adj[u]) {
			auto [v, i] = e;

			if (used[i]) continue;
			used[i] = 1;

			deg[v]--;
			if (deg[v] == 0) q.push(v);

			x = W[i];
		}

		if (u < M) BAL += x;
		else BAL -= x;
	}

	for(int i = 0; i < N; i++) {
		if (deg[i] == 0) continue;
		if (deg[i] != 2) {
			cout << "NO" << nl;
			exit(0-0);
		}
	}

	int bal = 0;
	function<void(int, int, int)> dfs = [&](int u, int p, int d) {
		vis[u] = 1;
		for(auto& e : adj[u]) {
			auto [v, i] = e;
			if (used[i]) continue;
			// cout << d << endl;
			bal += d * W[i];
			// cout << u << " -> " << v << " C " << W[i] << endl;
			used[i] = 1; dfs(v, u, -d);
		}
	};

	vi X;
	for(int u = 0; u < N; u++) if (!vis[u]) {
		bal = 0; dfs(u, -1, 1); X.pb(abs(bal));
		// cout << bal << endl << endl;
	}

	B dp; dp[0] = 1;
	for(auto x : X) dp = (dp << x) | (dp >> x);

	for(int x = 0; x < nax*kax; x++) if (dp[x]) {
		// cout << x << endl;
		if (min(abs(x - BAL), abs(x + BAL)) <= K) {
			cout << "YES" << nl;
			exit(0-0);
		}
	}

	cout << "NO" << nl;

	exit(0-0);
} 	

• Subtask 1: 0 / 18
• Subtask 2: 0 / 30
• Subtask 3: 0 / 23
• Subtask 4: 0 / 29