Номер перестановки и обратно

#include<stdio.h>
#include<stack>
#include<math.h>
#include<iostream>
#include<algorithm>
#include<string.h>
#include<string>
#include<set>
#include<memory.h>
#include<vector>
#include<map>
#include<queue>
#include<iomanip>
#include<ctime>

#define forn(i, n) for (int i = 0; i < (n); i++)

using namespace std;
long long fact(int n) {
    return !n ? 1 : n * fact(n - 1);
}

bool u[10];

void kPermutation(long long n, long long k) {
    k--;
    for (int i = 1; i <= n; i++)
        u[i] = 0;
    for (int i = 0; i < n; i++) {
        int K = 0;
        long long res = k / fact(n - i - 1) + 1;
        for (int j = 1; j <= n; ++j)
            if (!u[j]) {
                K++;
                if (K == res) {
                    cout << j << ' ';
                    u[j] = 1;
                    break;
                }
            }
        k %= fact(n - i - 1);
    }
}

void numberPermutation() {
    vector <int> a;
    int n = 10;
    forn (i, n)
        a.push_back(i + 1);
    random_shuffle(a.begin(), a.end());
    forn (i, n)
        cout << a[i] << " ";
    cout << endl;
    long long res = 0;
    for (int i = 0; i < n; i++) {
        int tek = 0;
        for (int j = 1; j <= a[i]; ++j)
            if (!u[j])
                tek++;
        u[a[i]] = 1;
        res += (tek - 1) * fact(n - i - 1);
    }
    cout << res + 1 << endl;
}

int main() {
    srand(time(NULL));
    long long n, k;
    cin >> n >> k;
    kPermutation(n, k);
    cout << endl;
    forn (i, n)
        u[i] = false;
    numberPermutation();
    return 0;
}