Submission #668175

#	Time	Username	Problem	Language	Result	Execution time	Memory
668175		Sohsoh84	Boarding Passes (BOI22_passes)	C++17	100 / 100	613 ms	359740 KiB

passes

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<ll, ll> pll;

#define all(x)			(x).begin(),(x).end()
#define X			first
#define Y			second
#define sep			' '
#define endl			'\n'
#define debug(x)		cerr << #x << ": " <<  x << endl;

const ll MAXG = 15;
const ll MAXN = 1e5 + 10;
const ll INF = 4e18;

int ps[MAXG][MAXN], n;
ll tps[MAXG][MAXG][MAXN], tss[MAXG][MAXG][MAXN], dp[1 << MAXG]; // :)
vector<int> ind[MAXG];
string s;

inline ll check(int mask, int x, int ind) {
	ll ans = 0;
	for (int i = 0; i < MAXG; i++)
		if (mask & (1 << i))
			ans += tps[x][i][ind] + tss[x][i][ind + 1];
	
	return ans * 2 + tps[x][x][ind] + tss[x][x][ind + 1];
}

int main() {
	ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
	cin >> s;
	n = s.size();
	s = "." + s;

	for (int i = 0; i < MAXG; i++) ind[i].push_back(0);
	for (int i = 1; i <= n; i++) ind[s[i] - 'A'].push_back(i);

	for (int i = 0; i < MAXG; i++)
		for (int j = 1; j <= n; j++)
			ps[i][j] = ps[i][j - 1] + (int(s[j] - 'A') == i);
	
	for (int i = 0; i < MAXG; i++) {
		for (int j = 0; j < MAXG; j++) {
			for (int k = 1; k <= n; k++) {
				tps[i][j][k] = tps[i][j][k - 1];
				if (int(s[k] - 'A') == i)
					tps[i][j][k] += ps[j][k - 1];
			}

			for (int k = n; k > 0; k--) {
				tss[i][j][k] = tss[i][j][k + 1];
				if (int(s[k] - 'A') == i)
					tss[i][j][k] += ps[j][n] - ps[j][k];
			}
		}
	}

	for (int mask = 1; mask < (1 << MAXG); mask++) {
		dp[mask] = INF;
		for (int i = 0; i < MAXG; i++) {
			if (mask & (1 << i)) {
				int tmask = (mask ^ (1 << i)), l = 0, r = ind[i].size() - 1;
				while (l < r) {
					int mid = (l + r) >> 1;
					if (check(tmask, i, ind[i][mid]) >= check(tmask, i, ind[i][mid + 1])) l = mid + 1;
					else r = mid;	
				}

				dp[mask] = min(dp[mask], dp[tmask] + check(tmask, i, ind[i][l]));	
			}
		}
	}

	int mask = (1 << MAXG) - 1;
	cout << dp[mask] / 2 << "." << (dp[mask] % 2) * 5 << endl;
	return 0;
}

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