Submission #653211

#	Time	Username	Problem	Language	Result	Execution time	Memory
653211		Stickfish	Group Photo (JOI21_ho_t3)	C++17	100 / 100	855 ms	460 KiB

Main

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

struct bitr {
    void resize(int n) {
        t.resize(n);
        sz = n;
    }

    void add(int i, int x) {
        while (i < sz) {
            t[i] += x;
            i |= i + 1;
        }
    }

    int get(int i) {
        int ans = 0;
        while (i > -1) {
            ans += t[i];
            i &= i + 1;
            --i;
        }
        return ans;
    }

    int operator()(int l, int r) {
        return get(r - 1) - get(l - 1);
    }
    
 private:
     int sz;
     vector<int> t;
};

const int MAXN = 5001;
int a[MAXN];
int ra[MAXN];
int dp_[MAXN];
int* dp = dp_ + 1;

signed main() {
    int n;
    cin >> n;
    for (int i = 0; i < n; ++i)
        cin >> a[i];
    for (int i = 0; i < n; ++i)
        ra[--a[i]] = i;
    for (int i = 0; i < n; ++i)
        dp[i] = MAXN * MAXN;
    for (int i = -1; i < n; ++i) {
        bitr used;
        bitr nonused;
        used.resize(n);
        nonused.resize(n);
        for (int j = i + 1; j < n; ++j) {
            nonused.add(ra[j], 1);
        }
        int add = 0;
        for (int j = i + 1; j < n; ++j) {
            nonused.add(ra[j], -1);
            add += nonused.get(ra[j] - 1);
            add -= used(ra[j], n);
            add += used.get(ra[j]);
            used.add(ra[j], 1);
            dp[j] = min(dp[j], dp[i] + add);
        }
    }
    cout << dp[n - 1] << '\n';
}

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