Генерация перестановок

#include<stdio.h>
#include<stack>
#include<math.h>
#include<time.h>
#include<iostream>
#include<algorithm>
#include<string>
#include<set>
#include<iomanip>
#include<vector>
#include<map>
#include<cassert>
#include<queue>
#include <tuple>


using namespace std;

typedef long long li;
typedef long double ld;

#define forn(i, n) for (int i = 0; i < int(n); ++i)
#define pb push_back
#define mp make_pair
#define shek_shek _DEBUG
#define mt make_tuple
#define aaaa(n) get<(n)>(aaaa)
#define all(v) v.begin(),v.end()
#define EPS  1e-9
#define PI 3.1415926535897932384626433832795


typedef long long li;
typedef long double ld;
typedef pair <int, int> pt;

#define ALPH "123456789"
#define DEPTH (9)

char s[DEPTH];

bool used[DEPTH];

void rec (int x) {
    if (x == DEPTH) {
        printf("%s\n", s);
        return;
    }
    for (int i = 0; i < DEPTH; i++) {
        if (!used[i]) {
            used[i] = true;
            s[x] = ALPH[i];
            rec(x + 1);
            used[i] = false;
        }
    }
}



int main () {
#ifdef shek_shek
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    rec(0);
    return 0;
}