Submission #453674

#	Time	Username	Problem	Language	Result	Execution time	Memory
453674		hhhhaura	The Xana coup (BOI21_xanadu)	C++14	100 / 100	101 ms	20420 KiB

xanadu

#define wiwihorz
#pragma GCC optimize("Ofast")
#pragma loop-opt(on)
#include <bits/stdc++.h>

#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 INF 1000000000ll
#define MOD 1000000007
#define eps (1e-9)

using namespace std;

#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())

#ifdef wiwihorz
#define print(a...) cerr << "Line " << __LINE__ <<": ", kout("[" + string(#a) + "] = ", a)
void kout() {cerr << endl;}
void vprint(auto L, auto R) { cerr << *L << " \n"[next(L) == R], ++L;}
template<class T1, class ... T2> void kout(T1 a, T2 ... e) { cerr << a << " ", kout(e...); }
#else
#define print(...) 0
#define vprint(...) 0
#endif
namespace solver {
	int n;
	vector<int> a, dp[4];
	vector<vector<int>> mp;
	void init_(int _n) {
		n = _n;
		a.assign(n + 1, 0);
		mp.assign(n + 1, vector<int>());
		rep(i, 0, 3) dp[i].assign(n + 1, INF);
	}
	void dfs(int x, int par) {
		if(a[x]) dp[2][x] = 1, dp[1][x] = 0;
		else dp[3][x] = 1, dp[0][x] = 0;
		int cnt = 0;
		for(auto i : mp[x]) if(i != par) {
			dfs(i, x), cnt++;
			
		}
		if(!cnt) return;
		rep(i, 0, 3) {
			int cur = 0, mn = INF, bs = (i >> 1) & 1;
			int goal = ((i & 1) ^ ((i >> 1) & 1) ^ a[x]), y = 0;
			for(auto j : mp[x]) if(j != par) {
				if(dp[bs | 2][j] < dp[bs][j]) y ^= 1;
				cur += min(dp[bs | 2][j], dp[bs][j]);
				mn = min(mn, abs(dp[bs][j] - dp[bs | 2][j]));
			}
			if(goal ^ y) dp[i][x] = min(INF, cur + mn + ((i >> 1) & 1));
			else dp[i][x] = min(cur + ((i >> 1) & 1), INF);
		}
	}
};
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 x, y; cin >> x >> y;
		mp[x].push_back(y);
		mp[y].push_back(x);
	}
	rep(i, 1, n) cin >> a[i];
	dfs(1 ,1);
	int ans = min(dp[0][1], dp[2][1]);
	if(ans == INF) cout << "impossible\n";
	else cout << ans << "\n";
	return 0;
}

Compilation message (stderr)

xanadu.cpp:3: warning: ignoring '#pragma loop ' [-Wunknown-pragmas]
    3 | #pragma loop-opt(on)
      | 
xanadu.cpp:25:13: warning: use of 'auto' in parameter declaration only available with '-fconcepts-ts'
   25 | void vprint(auto L, auto R) { cerr << *L << " \n"[next(L) == R], ++L;}
      |             ^~~~
xanadu.cpp:25:21: warning: use of 'auto' in parameter declaration only available with '-fconcepts-ts'
   25 | void vprint(auto L, auto R) { cerr << *L << " \n"[next(L) == R], ++L;}
      |                     ^~~~

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 10 / 10
• Subtask 4: 40 / 40
• Subtask 5: 30 / 30