Submission #1260281

#	Time	Username	Problem	Language	Result	Execution time	Memory
1260281		tvgk	Group Photo (JOI21_ho_t3)	C++20	100 / 100	3147 ms	656 KiB

Main

#include<bits/stdc++.h>
using namespace std;
#define task "a"
#define se second
#define fi first
#define ll long long
#define ii pair<ll, ll>
const long mxN = 5e3 + 7;
const ll inf = 1e18 + 7;

int n, a[mxN], vt[mxN];
ll dp[mxN];

struct Segment
{
    int node[mxN * 4];

    void Reset(int j = 1, int l = 1, int r = n)
    {
        node[j] = 0;
        if (l == r)
            return;

        int mid = (l + r) / 2;
        Reset(j * 2, l, mid);
        Reset(j * 2 + 1, mid + 1, r);
    }

    void Upd(int vt, int j = 1, int l = 1, int r = n)
    {
        if (l > vt || vt > r)
            return;

        node[j]++;
        if (l == r)
            return;

        int mid = (l + r) / 2;
        Upd(vt, j * 2, l, mid);
        Upd(vt, j * 2 + 1, mid + 1, r);
    }

    int Get(int u, int v, int j = 1, int l = 1, int r = n)
    {
        if (u > r || l > v)
            return 0;

        if (u <= l && r <= v)
            return node[j];

        int mid = (l + r) / 2;
        return Get(u, v, j * 2, l, mid) + Get(u, v, j * 2 + 1, mid + 1, r);
    }
};
Segment tree[2];

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    //freopen(task".INP", "r", stdin);
    //freopen(task".OUT", "w", stdout);

    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        cin >> a[i];
        vt[a[i]] = i;
        dp[i] = inf;
    }

    for (int i = n; i >= 1; i--)
    {
        tree[1].Reset();
        ll cost = 0;
        for (int j = i; j >= 1; j--)
        {
            cost += n - vt[j] - tree[0].Get(vt[j] + 1, n);
            cost -= tree[1].Get(1, vt[j]);
            tree[1].Upd(vt[j]);

            dp[j] = min(dp[j], dp[i + 1] + cost);
        }
        tree[0].Upd(vt[i]);
    }
    cout << dp[1];
}

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 32 / 32
• Subtask 4: 20 / 20
• Subtask 5: 36 / 36