Submission #853288

#	Time	Username	Problem	Language	Result	Execution time	Memory
853288		NK_	Pipes (BOI13_pipes)	C++17	100 / 100	58 ms	16844 KiB

pipes

// 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;

int main() {
	cin.tie(0)->sync_with_stdio(0);

	int N, M; cin >> N >> M;

	if (M > N) {
		cout << 0 << nl;
		exit(0-0);
	}

	// TREE OR 1 CYCLE

	vl A(N); for(auto& x : A) cin >> x;

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

	vl ans(M); vi vis(N);
	function<int(int)> fix = [&](int u) { // remove odd
		vis[u] = 1;
		for(auto v : adj[u]) if (!vis[v.f]) {
			ans[v.s] = fix(v.f);
			A[u] -= ans[v.s];
		}

		int need = (A[u] % 2 == 0 ? 0 : 1); A[u] -= need;
		return need;
	};

	if (fix(0)) {
		cout << 0 << nl;
		exit(0-0);
	}	



	vi deg(N); vi seen(N);
	for(int u = 0; u < N; u++) for(auto v : adj[u]) {
		if (u > v.f) deg[u]++, deg[v.f]++;
	}

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

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

		seen[u] = 1;
		for(auto& v : adj[u]) {
			if (!seen[v.f]) {
				deg[v.f]--; 
				ans[v.s] += A[u]; A[v.f] -= A[u]; A[u] = 0;
				if (deg[v.f] == 1) q.push(v.f);
			}
		}
	}

	// for(int i = 0; i < M; i++) cout << ans[i] << nl;
	// cout << nl;
	// for(int i = 0; i < N; i++) cout << A[i] << nl;
	// cout << nl;


	int len = count(begin(seen), end(seen), 0);

	if (len == 0) {
		for(int i = 0; i < M; i++) cout << ans[i] * 2LL << nl;
		exit(0-0);
	}

	if (len % 2 == 0) {
		cout << 0 << nl;
		exit(0-0);
	}	

	
	vi P;
	function<void(int)> dfs = [&](int u) {
		if (sz(P) == 2*len) return;
		P.pb(u);
		for(auto& v : adj[u]) {
			if (seen[v.f]) continue;
			if (sz(P) > 1 && v.s == P[sz(P)-2]) continue;
			P.pb(v.s); 
			dfs(v.f);
			if (sz(P) == 2*len) return;
		}
	};

	int r = find(begin(seen), end(seen), 0) - begin(seen);
	dfs(r);

	int amt = 0, coef = 1;
	for(int i = 0; i < 2 * len; i += 2) {
		amt += coef * A[P[i]]; coef = -coef;
	}

	amt /= 2;

	for(int i = 0; i < 2 * len; i += 2) {
		ans[P[i+1]] += A[P[i]] - amt;
		amt = A[P[i]] - amt ;
	}

	for(int i = 0; i < M; i++) cout << ans[i] * 2LL << nl;
	exit(0-0);
} 	

• Subtask 1: 30 / 30
• Subtask 2: 70 / 70