Submission #387708

#	Time	Username	Problem	Language	Result	Execution time	Memory
387708		casperwang	Cheerleaders (info1cup20_cheerleaders)	C++14	100 / 100	1760 ms	9456 KiB

cheerleaders

#include <bits/stdc++.h>
#pragma gcc optimize("Ofast")
#define ll long long
#define pb emplace_back
#define All(x) x.begin(), x.end()
#define pii pair<int,int>
#define ff first
#define ss second
using namespace std;
#define debug(args...) kout("[ " + string(#args) + " ]", args)
void kout() { cerr << endl; }
template <class T, class ...U> void kout(T a, U ...b) { cerr << a << ' ',kout(b...); }
template <class T> void pary(T L, T R) { while (L != R) cerr << *L << " \n"[++L==R]; }

const int MAXN = 17;
int N, M;
ll ans;
pii op;
string ops;
vector <int> a, c;
vector <ll> val;

inline int lb(int a) {
	return a &- a;
}

void init() {
	a.resize(M);
	c.resize(M);
	val.resize(N);
}

class Bit {
	private:
		int arr[1<<MAXN+1];
	public:
		inline void mdy(int a, int k) {
			for (int i = a; i <= M; i+=lb(i))
				arr[i] += k;
		}
		inline int qry(int a) {
			int s = 0;
			for (int i = a; i; i-=lb(i))
				s += arr[i];
			return s;
		}
} bit;

ll cnt_inv(vector <int> c) {
	ll s = 0;
	vector <int> del;
	for (int i = 0; i < M; i++) {
		s += i - bit.qry(c[i]);
		bit.mdy(c[i]+1, 1);
	}
	for (int i = 0; i < M; i++)
		bit.mdy(i+1, -1);
	return s;
}

void build() {
	for (int i = 0; i < N; i++) {
		vector <vector<int>> arr(1<<(N-i));
		for (vector<int> &v : arr) v.reserve(1<<i);
		val[i] = 0;
		for (int j = 0; j < M; j++)
			arr[c[j]/(1<<i)].pb(j);
		for (int j = 0; j < (1<<(N-i)); j+=2) {
			for (int k : arr[j+1]) {
				val[i] += arr[j].end() - lower_bound(All(arr[j]), k);
			}
		}
	}
}

string solve(pii op) {
	string str;
	for (int i = 0; i < op.ff; i++)
		str.push_back('2');
	for (int i = 0; i < N; i++) {
		str.push_back('2');
		if ((1<<i) & op.ss) {
			str.push_back('1');
		}
	}
	return str;
}

signed main() {
	ios_base::sync_with_stdio(0), cin.tie(0);
	cin >> N;
	M = (1<<N);
	init();
	for (int i = 0; i < M; i++)
		cin >> a[i], c[a[i]] = i;
	ans = cnt_inv(c);
	for (int j = 0; j < N; j++) {
		build();
		ll sum = cnt_inv(c);
		int x = 0;
		for (int i = 1; i < M; i++) {
			int p = lb(i);
			x ^= p;
			ll O = (ll) M * p / 2;
			sum += O - 2 * val[__lg(p)];
			val[__lg(p)] = O - val[__lg(p)];
			if (sum < ans) {
				ans = sum, op = pii(j, x);
			}
		}
		for (int i = 0; i < M; i++) {
			c[i] = M / 2 * (c[i] & 1) + c[i] / 2;
		}
	}
	cout << ans << '\n';
	cout << solve(op) << '\n';
	return 0;
}

Compilation message (stderr)

cheerleaders.cpp:2: warning: ignoring #pragma gcc optimize [-Wunknown-pragmas]
    2 | #pragma gcc optimize("Ofast")
      | 
cheerleaders.cpp:35:18: warning: suggest parentheses around '+' inside '<<' [-Wparentheses]
   35 |   int arr[1<<MAXN+1];
      |              ~~~~^~

• Subtask 1: 16 / 16
• Subtask 2: 10 / 10
• Subtask 3: 25 / 25
• Subtask 4: 21 / 21
• Subtask 5: 28 / 28