Submission #748643

#	Time	Username	Problem	Language	Result	Execution time	Memory
748643		inventiontime	Boarding Passes (BOI22_passes)	C++17	60 / 100	2078 ms	3524 KiB

passes

#include <bits/stdc++.h>
using namespace std;

#define int ll
#define endl '\n' //comment for interactive
#define fast_io ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)

#define pb push_back
#define re resize
#define ff first
#define ss second

#define all(x) (x).begin(), (x).end()
#define all1(x) (x).begin()+1, (x).end()
#define loop(i, n) for(int i = 0; i < n; i++)
#define loop1(i, n) for(int i = 1; i <= n; i++)

#define print(x) cout << #x << ": " << x << endl << flush

typedef long long ll;
typedef vector<int> vi;
typedef vector<double> vd;
typedef array<int, 2> ii;
typedef array<int, 3> ti;
typedef vector<ii> vii;
typedef vector<ti> vti;
typedef vector<vi> vvi;
typedef priority_queue<int> pq;

template<class T> bool ckmin(T&a, T b) { bool B = a > b; a = min(a, b); return B; }
template<class T> bool ckmax(T&a, T b) { bool B = a < b; a = max(a, b); return B; }

const int inf = 1e17;

double cst(int x) {
    return (double) x * (x-1) / 4;
}

void solve() {


    string s;
    cin >> s;
    int n = s.size();
    vvi pos(26);
    loop(i, n) 
        pos[s[i]-'A'].pb(i);
    vi ch;
    loop(i, 26) if(!pos[i].empty())
        ch.pb(i);
    int g = ch.size();
    vi id(26);
    loop(i, g) id[ch[i]] = i;

    if(g == 1) {
        cout << setprecision(16) << cst(n/2) + cst((n+1)/2) << endl;
        return;
    }


    vd dp(1 << g, inf);
    dp[0] = 0;
    loop(pre, 1 << g) {
        bitset<15> prev(pre);
        loop(ch, g) if(!prev[ch]) {
            int nxt = pre + (1 << ch);
            double cost = inf;

            vd left(n);
            vd right(n+1);
            int cnt = 0, oth = 0;
            for(int i = 0; i < n; i++) {
                if(i) left[i] = left[i-1];
                if(prev[id[s[i]-'A']]) oth++;
                else if(id[s[i]-'A'] == ch) {
                    cnt++;
                    left[i] += oth;
                    left[i] += cst(cnt);
                    left[i] -= cst(cnt-1);
                }
            }
            cnt = 0, oth = 0;
            for(int i = n-1; i >= 0; i--) {
                right[i] = right[i+1];
                if(prev[id[s[i]-'A']]) oth++;
                else if(id[s[i]-'A'] == ch) {
                    cnt++;
                    right[i] += oth;
                    right[i] += cst(cnt);
                    right[i] -= cst(cnt-1);
                }
            }

            loop(i, n)
                ckmin(cost, left[i] + right[i+1]);

            ckmin(dp[nxt], dp[pre] + cost);
        }
    }


    cout << setprecision(16) << dp[(1 << g) - 1] << endl;

}

signed main() {

    fast_io;

    int t = 1; //cin >> t;
    while(t--)
        solve();

    return 0;

}

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