nikhil.cpp

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

void makeCombiUtil(vector<vector<int>> &ans,
                   vector<int> &tmp, int n, int left, int k)
{
    // Pushing this vector to a vector of vector
    if (k == 0)
    {
        ans.push_back(tmp);
        return;
    }

    // i iterates from left to n. First time
    // left will be 1
    for (int i = left; i <= n; ++i)
    {
        tmp.push_back(i);
        makeCombiUtil(ans, tmp, n, i + 1, k - 1);

        // Popping out last inserted element
        // from the vector
        tmp.pop_back();
    }
}

// Prints all combinations of size k of numbers
// from 1 to n.
vector<vector<int>> makeCombi(int n, int k)
{
    vector<vector<int>> ans;
    vector<int> tmp;
    makeCombiUtil(ans, tmp, n, 1, k);
    return ans;
}

// Driver code
int main()
{
    // given number
    int n;
    int k;
    cin >> n >> k;
    '' vector<vector<int>> ans = makeCombi(n, k);
    for (int i = 0; i < ans.size(); i++)
    {
        for (int j = 0; j < ans[i].size(); j++)
        {
            cout << ans.at(i).at(j) << " ";
        }
        cout << endl;
    }
    return 0;
}