1-Recursion-Basic

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

void solve(int n)
{
    if(n==0) return;
    solve(n-1);
    cout<< n << " ";
}


int main()
{
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    int n; cin>>n;
    solve(n);
    return 0;
}

input
======
3
output
=======
1 2 3

2-Tree-Recursion

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

void solve(int n)
{
    if(n==0) return;
    cout<< n << " ";
    solve(n-1);
    solve(n-1);
}


int main()
{
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    int n; cin>>n;
    solve(n);
    return 0;
}

input
======
3
output
=======
3 2 1 1 2 1 1