Submission #853663

#	Time	Username	Problem	Language	Result	Execution time	Memory
853663		NK_	Tug of War (BOI15_tug)	C++17	100 / 100	1702 ms	10576 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;
const int ZERO = nax * kax;
using B = bitset<2 * ZERO>;
 
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<set<pi>> 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].insert(mp(v, i));
		adj[v].insert(mp(u, i));
	}

	queue<int> q; for(int i = 0; i < N; i++) {
		if (!sz(adj[i])) {
			cout << "NO" << nl;
			exit(0-0);
		}

		if (sz(adj[i]) == 1) q.push(i);
	}

	int BAL = 0;
	while(sz(q)) {
		int u = q.front(); q.pop();

		pi e = *begin(adj[u]);
		adj[u].clear();

		adj[e.f].erase(mp(u, e.s));

		if (u < M) BAL += W[e.s];
		else BAL -= W[e.s];

		if (sz(adj[e.f]) == 1) q.push(e.f);
	}

	for(int i = 0; i < N; i++) {
		if (sz(adj[i]) == 0) continue;
		if (sz(adj[i]) != 2) {
			cout << "NO" << nl;
			exit(0-0);
		}
	}
 
	int bal = 0;
	function<void(int, int)> dfs = [&](int u, int d) {
		if (sz(adj[u])) {
			pi e = *begin(adj[u]);
			adj[u].clear();
			adj[e.f].erase(mp(u, e.s));
			// cout << u << " " << e.s << endl;
			bal += d * W[e.s];
			dfs(e.f, -d);
		}
	};

	vi X;
	for(int u = 0; u < M; u++) if (sz(adj[u])) {
		bal = 0; dfs(u, 1); X.pb(abs(bal));
	}

	B dp; dp[ZERO + BAL] = 1;
	for(auto x : X) if (x) {
		dp = (dp << x) | (dp >> x);
	}

	for(int x = 0; x < 2*ZERO; x++) if (dp[x]) {
		// cout << x << endl;
		if (abs(x - ZERO) <= K) {
			cout << "YES" << nl;
			exit(0-0);
		}
	}

	cout << "NO" << nl;

	exit(0-0);
} 	 

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