subsequence.cpp

#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define ull unsigned long long
#define ff first
#define ss second
#define mp make_pair
#define pb push_back

const int N = 2e5 + 11;

int n;
int li[10];

void subs(vector<int> v, int k) {
	if (k == n) {
		for (auto x : v)cout << x << " ";
		cout << endl;
	} else {
		subs(v, k + 1);
		v.push_back(li[k]);
		subs(v, k + 1);
		v.pop_back();
	}
}


// Itereative
// for (int b = 0; b < (1<<n); b++) {
// vector<int> subset;
// for (int i = 0; i < n; i++) {
// if (b&(1<<i)) subset.push_back(i);
// }
// }

void solve() {
	cin >> n;
	for (int i = 0; i < n; i++)cin >> li[i];
	vector<int> sub;
	subs(sub, 0);
}

int main() {
	freopen("input.txt", "r", stdin);
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int no_of_test_cases;
	// cin >> no_of_test_cases;
	no_of_test_cases = 1;
	while (no_of_test_cases--) solve();
	return 0;
}


// Second way

class Solution {
    void traverse(vector<int>& nums, 
                  vector<int>& calc, 
                  vector<vector<int>> &res, 
                  int numberTaken) {
        
        if (numberTaken == size(nums)) {
            res.push_back(calc);
            return;
        }
        
        calc.push_back(nums[numberTaken]);
        traverse(nums, calc, res, numberTaken + 1);
        calc.pop_back();
        traverse(nums, calc, res, numberTaken + 1);
    }
    
public:
    vector<vector<int>> subsets(vector<int>& nums) {
        vector<vector<int>> res;
        vector<int> calc;
        traverse(nums, calc, res, 0);
        return res;
    }
};