Submission #723396

#	Time	Username	Problem	Language	Result	Execution time	Memory
723396		drdilyor	Boarding Passes (BOI22_passes)	C++17	60 / 100	2099 ms	377004 KiB

passes

#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define time(code) {auto _s = chrono::high_resolution_clock::now(); code;cerr << (chrono::high_resolution_clock::now() - _s).count() / 1e9 << '\n';}
 
inline ll exp_inv(ll x) {
    return x * (x-1);
}
 
int main() {
    cin.tie(0)->sync_with_stdio(0);
    char a = 'A';
    string s; cin >> s;
    const int G = 15, N = 1e5;
    int n = s.size();
    if (n == 1) {
        cout << "0\n";
        return 0;
    }

    ll suml[G][G][N];
    ll sumr[G][G][N];
    ll cr[G][N];
    ll cl[G][N];
    int cnt[G]{};
    vector ix(G, vector<int>());

    time(({
        for (int c1 = 0; c1 < G; c1++) {
            for (int c2 = 0; c2 < G; c2++) {
                ll res = 0, cur = 0;
                for (int i = 0; i < n; i++) {
                    if (s[i] == c1+a)
                        res += cur;
                    else if (s[i] == c2+a)
                        cur++;
                    suml[c1][c2][i] = res;
                }
            }
        }
        for (int c1 = 0; c1 < G; c1++) {
            for (int c2 = 0; c2 < G; c2++) {
                ll res = 0, cur = 0;
                for (int i = n-1; i >= 0; i --) {
                    if (s[i] == c1+a)
                        res += cur;
                    else if (s[i] == c2+a)
                        cur++;
                    sumr[c1][c2][i] = res;
                }
            }
        }
        for (int j = 0; j < G; j++) {
            int c = 0;
            for (int i = 0; i < n;i ++) {
                if (s[i] == j+a)
                    c++;
                cl[j][i] = c;
            }
        }
        for (int j = 0; j < G; j++) {
            int c = 0;
            for (int i = n-1; i >= 0; i--) {
                if (s[i] == j+a)
                    c++;
                cr[j][i] = c;
            }
        }
        for (int i = 0; i < n; i++)
            cnt[s[i] - a]++;
        for (int i = 0; i < G; i++)
            ix[i].reserve(cnt[i]);
        for (int i = 0; i < n ;i++) 
            ix[s[i] - a].push_back(i);
    }));


    ll memo[1<<G];
    memo[(1<<G)-1] = 0;
    for (int used = (1<<G)-1-1; used >= 0; used--) {
        ll& res = memo[used];
        res = 1e18;
        for (int i = 0 ;i < G; i++) {
            if (used&1<<i) continue;

            auto f = [&](int i, int j) {
                ll sum = 0;
                if (j)
                    for (int c2 = 0; c2 < G; c2++)
                        sum += (used>>c2&1) * suml[i][c2][j-1];
                if (j < n)
                    for (int c2 = 0; c2 < G; c2++)
                        sum += (used>>c2&1) * sumr[i][c2][j];
                return sum * 4 + (j < n ? exp_inv(cr[i][j]) : 0) + (j ? exp_inv(cl[i][j-1]) : 0);
            };

            int l = -1, r = (int)ix[i].size()-2;
            while (l < r-1) {
                int m = (l+r) / 2;
                ll a = f(i, ix[i][m]), b = f(i, ix[i][m+1]);
                if (a == b) break;
                else if (a < b) r = m;
                else l = m;
            }
 
            ll cur = min(f(i, 0), f(i, n));;
            for (int j = max(l-1, 0); j < min((int)ix[i].size(), 2 + max(0, r)); j++) {
                cur = min(cur, f(i, ix[i][j]));
            }
            res = min(res, cur + memo[used|1<<i]);
        }
    };
    ll ans;
    ans = memo[0];
 
    cout << ans / 4;
    if (ans%4 == 1) cout << ".25";
    if (ans%4 == 2) cout << ".5";
    if (ans%4== 3) cout << ".75";
    cout << endl;
}

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