Submission #428365

#	Time	Username	Problem	Language	Result	Execution time	Memory
428365		oolimry	Cheerleaders (info1cup20_cheerleaders)	C++17	54 / 100	669 ms	25756 KiB

cheerleaders

#include <bits/stdc++.h>
using namespace std;
#define sz(x) (int) (x).size()
#define all(x) (x).begin(), (x).end()
#define show(x) cerr << #x << " is " << x << endl;
#define show2(x,y) cerr << #x << " is " << x << " " << #y << " is " << y << endl;
#define show3(x,y,z) cerr << #x << " is " << x << " " << #y << " is " << y << " " << #z << " is " << z << endl;
#define tern(cond, a, b) (cond ? a : b)
typedef long long lint;
typedef pair<lint,lint> ii;

vector<int> original;
vector<int> arr[140005];
vector<int> nxt;
vector<int> temp;

lint ans = 123123231232132LL;
lint res = 0;

int main(){
	ios_base::sync_with_stdio(false); cin.tie(0);
	
	int n; cin >> n;
	int N = (1<<n);
	original.resize(N);
	for(int i = 0;i < N;i++) cin >> original[i];
	
	if(n == 0){
		cout << 0;
		return 0;
	}
	
	for(int iter = 0;iter < n;iter++){
		for(int i = 0;i < N;i++) arr[i].clear();
		for(int i = 0;i < N;i++) arr[i].push_back(original[i]);
		
		res = 0;
		
		for(lint gap = 1;gap < N;gap *= 2){
			lint invcnt = 0;
			lint total = 0;
			
			for(int s = 0;s < N;s += 2*gap){
				int m = s+gap, e = s+2*gap;
				lint l = 0;
				for(int r : arr[m]){
					while(l < sz(arr[s])){
						if(arr[s][l] > r) break;
						else l++;
					}
					invcnt += l;
				}
				total += gap*gap;
				
				swap(temp, arr[s]);
				arr[s].resize(sz(temp) + sz(arr[m]));
				merge(all(temp), all(arr[m]), arr[s].begin());
				temp.clear();
			}

			if(total-invcnt < invcnt){
				res += total-invcnt;
			}
			else{
				res += invcnt;
			}
		}
		
		//show(res);
		ans = min(ans, res);
		
		//for(int i = 0;i < N;i++) cerr << original[i] << " "; cerr << endl;
		//for(int i = 0;i < N;i++) cerr << original[i] << " "; cerr << endl;
		
		nxt.clear();
		for(int i = 0;i < N;i += 2) nxt.push_back(original[i]);
		for(int i = 1;i < N;i += 2) nxt.push_back(original[i]);
		swap(nxt, original);
	}
	
	cout << ans;
}

Compilation message (stderr)

cheerleaders.cpp: In function 'int main()':
cheerleaders.cpp:44:20: warning: unused variable 'e' [-Wunused-variable]
   44 |     int m = s+gap, e = s+2*gap;
      |                    ^

• Subtask 1: 8 / 16
• Subtask 2: 5 / 10
• Subtask 3: 20 / 25
• Subtask 4: 0 / 21
• Subtask 5: 21 / 28