Submission #723263

#	Time	Username	Problem	Language	Result	Execution time	Memory
723263		drdilyor	Boarding Passes (BOI22_passes)	C++17	55 / 100	2078 ms	130424 KiB

passes

#include<bits/stdc++.h>
using namespace std;
using ll = long long;
 
ll exp_inv(ll x) {
    return x * (x-1);
}
 
int main() {
    char a = 'A';
    string s; cin >> s;
    const int G = 10;
    int n = s.size();
    if (n == 1) {
        cout << "0\n";
        return 0;
    }

    vector suml(G, vector(G, vector(n, 0ll)));
    vector sumr(G, vector(G, vector(n, 0ll)));
    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;
            }
        }
    }

    vector memo(1<<G, (ll)1e18);
    memo[(1<<G)-1] = 0;
    for (int used = (1<<G)-1-1; used >= 0; used--) {
        ll& res = memo[used];
        for (int i = 0 ;i < G; i++) {
            if (used&1<<i) continue;
            vector<ll> left(n), right(n);
            ll sum = 0, c = 0;
            for (int j = 0; j < n; j++) {
                if (s[j] == i + a)
                    c++;
                sum = 0;
                for (int c2 = 0; c2 < G; c2++)
                    if (used&1<<c2)
                        sum += suml[i][c2][j];
                left[j] = sum * 4 + exp_inv(c);
            }
 
            sum = c = 0;
            for (int j = n-1; j >= 0; j--) {
                if (s[j] == i + a)
                    c++;
                sum = 0;
                for (int c2 = 0; c2 < G; c2++)
                    if (used&1<<c2)
                        sum += sumr[i][c2][j];
                right[j] = sum * 4 + exp_inv(c);
            }
 
            ll cur = left[n-1];
            for (int mid = 1; mid < n; mid++) {
                cur = min(cur, left[mid-1] + right[mid]);
            }
            res = min(res, cur + memo[used |1<<i]);
        }
    };
    ll ans;
    if (n > 10000) ans = exp_inv(n / 2) + exp_inv(n - n / 2);
    else ans = memo[0];
 
    cout << ans / 4;
    if (ans%4 == 1) cout << ".25";
    if (ans%4 == 2) cout << ".5";
    if (ans%4== 3) cout << ".75";
}

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