C++の最初のn個の自然数から長さkの増加するすべてのシーケンスを出力します

#include<iostream>
using namespace std;
void printSequence(int arr[], int k) {
   for (int i=0; i<k; i++)
      cout<<arr[i]<<" ";
   cout<<endl;
}
void printKLengthSequence(int n, int k, int &len, int arr[]) {
   if (len == k) {
      printSequence(arr, k);
      return;
   }
   int i = (len == 0)? 1 : arr[len-1] + 1;
   len++;
   while (i<=n) {
      arr[len-1] = i;
      printKLengthSequence(n, k, len, arr);
      i++;
   }
   len--;
}
void generateSequence(int n, int k) {
   int arr[k];
   int len = 0;
   printKLengthSequence(n, k, len, arr);
}
int main() {
   int k = 3, n = 4;
   cout<<"Sequence of length "<<k<<" generated using first "<<n<<" natural numbers :\n";
   generateSequence(n, k);
   return 0;
}

A sequence of length 3 generated using first 4 natural numbers −
1 2 3
1 2 4
1 3 4
2 3 4