Submission #1122186

#	Time	Username	Problem	Language	Result	Execution time	Memory
1122186		vjudge1	Group Photo (JOI21_ho_t3)	C++17	100 / 100	353 ms	196520 KiB

Main

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <queue>
#include <ctime>
#include <cassert>
#include <complex>
#include <string>
#include <cstring>
#include <chrono>
#include <random>
#include <bitset>
#include <fstream>
#include <array>
#include <functional>
#include <stack>
#include <memory>
#ifdef LOCAL
#define _GLIBCXX_DEBUG
#endif

using namespace std;

#define int long long
#define app push_back
#define all(x) x.begin(), x.end()
#ifdef LOCAL
#define debug(...) [](auto...a){ ((cout << a << ' '), ...) << endl; }(#__VA_ARGS__, ":", __VA_ARGS__)
#define debugv(v) do { cout << #v << ": "; for (auto x : v) cout << x << ' '; cout << endl; } while(0)
#else
#define debug(...)
#define debugv(v)
#endif

int32_t main() {
    cin.tie(0);ios_base::sync_with_stdio(0);
    int n;
    cin >> n;
    vector <int> h(n), q(n + 1);
    for (int i = 0; i < n; ++i) {
    	cin >> h[i];
    	h[i]--;
    	q[h[i]]=i;
    }
    vector <vector <int> > pre(n + 1, vector <int> (n + 1));
    for (int x = 0; x < n; ++x) {
    	for (int y = 0; y < x; ++y) {
    		if (q[x] < q[y]) {
    			pre[x + 1][y + 1]++;
    		}
    	}
    }
    for (int i = 0; i < n; ++i) {
    	for (int j = 0; j < n; ++j) {
    		pre[i + 1][j + 1] += pre[i + 1][j] + pre[i][j + 1] - pre[i][j];
    	}
    }

    auto inv = [&] (int y1, int y2, int x1, int x2) {
    	return pre[x2][y2] - pre[x1][y2] - pre[x2][y1] + pre[x1][y1];
    };

    auto c2 = [&] (int k) {
    	return k * (k - 1) / 2;
    };

    vector <int> dp(n + 1, n * n);
    dp.front() = 0;
    for (int l = 0; l < n; ++l) {
    	for (int r = l + 1; r <= n; ++r) {
    		dp[r] = min(dp[r], dp[l] + inv(0, l, l, r) + (c2(r - l) - inv(l, r, l, r)));
    	}
    }
    cout << dp.back() << '\n';
}

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