Submission #1264383

#	Time	Username	Problem	Language	Result	Execution time	Memory
1264383		badge881	Boarding Passes (BOI22_passes)	C++20	100 / 100	210 ms	21580 KiB

passes

#include <bits/stdc++.h>
#define len(s) (ll) s.size()
using namespace std;

typedef long long ll;
typedef long double ld;

const int N = 2e5 + 11;
const int MAX = 1e6;
const long long inf = 1e18 + 10;

ll n;
ll a[N], dp[(1 << 16)], pr[30][N], sf[30][N], cnt[30][30][N];

string s, t;

vector<ll> g[N];

ll f(ll x, ll pos, ll msk)
{
    ll ans = pos * (pos - 1) / 2 + (len(g[x]) - pos) * (len(g[x]) - pos - 1) / 2;
    for (ll y = 0; y < 15; y++)
        if (x != y && (msk >> y & 1))
            ans += cnt[x][y][pos] * 2;
    return ans;
}

int main()
{
    cin >> s, n = len(s);
    for (ll i = 0; i < n; i++)
        a[i] = s[i] - 'A', g[a[i]].push_back(i);
    for (ll x = 0; x < 15; x++)
    {
        for (ll y = 0; y < 15; y++)
        {
            if (x == y)
                continue;
            for (ll i = 0; i < len(g[x]) + 10; i++)
                pr[x][i] = sf[x][i] = 0;
            for (ll i = 0, j = 0; i < len(g[x]); i++)
            {
                while (j < len(g[y]) && g[y][j] <= g[x][i])
                    j++;
                pr[x][i + 1] = pr[x][i] + j;
            }
            for (ll i = len(g[x]) - 1, j = len(g[y]) - 1; i >= 0; i--)
            {
                while (j >= 0 && g[y][j] >= g[x][i])
                    j--;
                sf[x][i + 1] = sf[x][i + 2] + len(g[y]) - j - 1;
            }
            for (ll i = 0; i <= len(g[x]); i++)
                cnt[x][y][i] = pr[x][i] + sf[x][i + 1];
        }
    }
    for (ll msk = 1; msk < (1 << 15); msk++)
    {
        dp[msk] = inf;
        for (ll i = 0; i < 15; i++)
        {
            if ((msk >> i & 1))
            {
                dp[msk] = min(dp[msk], dp[(msk ^ (1 << i))] + f(i, 0, msk));
                ll l = 1, r = len(g[i]);
                while (r - l > 1)
                {
                    ll middle = (l + r) / 2;
                    if (f(i, middle, msk) > f(i, middle + 1, msk))
                        l = middle;
                    else
                        r = middle;
                }
                for (ll j = l; j <= r; j++)
                    dp[msk] = min(dp[msk], dp[(msk ^ (1 << i))] + f(i, j, msk));
            }
        }
    }
    ll ans = dp[(1 << 15) - 1];
    if (ans % 2)
        cout << ans / 2 << ".5";
    else
        cout << ans / 2;
}

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