Generate All Possible Combinations and Permutations of a Sequence with Length of N using C++

#include <bits/stdc++.h>

using namespace std;

vector<vector<int>> res;

void Generate(vector<int>& vec, int n, int i = 0) {
    if (i == n) {
        res.push_back(vec);
        return;
    }
    for (auto num : {0, 1, 2}) {
        vec[i] = num;
        Generate(vec, n, i + 1);
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n = 5;
    vector<int> vec(n);
    // generate sequence of length n using the given elements: {0, 1, 2}
    Generate(vec, n);
    for (int i = 0; i < (int) res.size(); i++) {
        for (int j = 0; j < (int) res[i].size(); j++) {
            cout << res[i][j] << " ";
        }
        cout << '\n';
    }
    return 0;
}