Submission #578165

#	Time	Username	Problem	Language	Result	Execution time	Memory
578165		8e7	Boarding Passes (BOI22_passes)	C++17	60 / 100	705 ms	2192 KiB

passes

//Challenge: Accepted
#include <bits/stdc++.h>
using namespace std;
#ifdef zisk
void debug(){cout << endl;}
template<class T, class ... U> void debug(T a, U ... b){cout << a << " ", debug(b...); }
template<class T> void pary(T l, T r) {
	while (l != r) cout << *l << " ", l++;
	cout << endl;
}
#else
#define debug(...) 0
#define pary(...) 0
#endif
#define ll long long
#define maxn 100005
#define maxc 10
#define pii pair<int, int>
#define ff first
#define ss second
#define io ios_base::sync_with_stdio(0);cin.tie(0);
const ll inf = 1LL<<60;
ll dp[1<<maxc];
int pref[maxn], suf[maxn], col[maxn];
vector<int> pos[maxc];
int main() {
	io
	ll n;
	string s;
	cin >> s;
	n = s.size();
	/*
	ll p = n / 2;
	cout << fixed << setprecision(5) << (double)(p * (p - 1) + (n-p) * (n-p - 1)) / 4 << "\n";
	return 0;
	*/
	for (int i = 0;i < n;i++) {
		int c = s[i] - 'A';
		pos[c].push_back(i);	
		col[i] = c;
	}
	for (int i = 0;i < (1<<maxc);i++) dp[i] = inf;
	dp[0] = 0;
	for (int i = 0;i < (1<<maxc);i++) {
		for (int j = 0;j < n;j++) {
			pref[j] = suf[j] = (i >> col[j])&1;
			pref[j] += j ? pref[j-1] : 0;
		}
		for (int j = n - 2;j >= 0;j--)suf[j] += suf[j+1];
		for (int j = 0;j < maxc;j++) {
			if (!((i >> j) & 1)) {
				ll cur = 0, pc = 0, sc = 0;		
				for (int k:pos[j]) {
					cur += pref[k];
					pc++;
				}
				int to = i + (1<<j);
				dp[to] = min(dp[to], dp[i] + cur*4 + pc * (pc-1));
				for (int k = (int)pos[j].size() - 1;k >= 0;k--) {
					sc++;
					pc--;
					cur += suf[pos[j][k]] - pref[pos[j][k]];
					dp[to] = min(dp[to], dp[i] + cur*4 + pc * (pc-1) + sc * (sc-1));
				}
			}
		}
	}
	ll ans = dp[(1<<maxc) - 1];
	ll a0 = ans / 4;
	cout << a0;
	if (ans % 4 == 1) {
		cout << ".25\n";
	} else if (ans % 4 == 2) {
		cout << ".5\n";
	} else if (ans % 4 == 3) {
		cout << ".75\n";
	}
}

• Subtask 1: 5 / 5
• Subtask 2: 25 / 25
• Subtask 3: 30 / 30
• Subtask 4: 0 / 40