C++ Program to Generate All Possible Combinations of a Given List of Numbers

This is a C++ program to generate all possible combinations of a given list of numbers

Algorithms

Begin
   Take the number of elements and the elements as input.
   function Combi(char a[], int reqLen, int s, int currLen, bool check[], int l) :
   If currLen>reqLen then
   Return
   Else if currLen=reqLen then
      Then print the new generated sequence.
   If s=l then
      Then return no further element is left.
   For every index there are two option:
   either proceed with a start as ‘true’ and recursively call Combi() with incremented value of ‘currLen’ and ‘s’.
   Or proceed with a start as ‘false’ and recursively call Combi() with only incremented value of ‘s’.
End

Example

#include<iostream>
using namespace std;
void Combi(char a[], int reqLen, int s, int currLen, bool check[], int l)
// print the all possible combination of given array set
{
   if(currLen > reqLen)
   return;
   else if (currLen == reqLen) {
      cout<<"\t";
      for (int i = 0; i < l; i++) {
         if (check[i] == true) {
            cout<<a[i]<<" ";
         }
      }
      cout<<"\n";
      return;
   }
   if (s == l) {
      return;
   }
   check[s] = true;
   Combi(a, reqLen, s + 1, currLen + 1, check, l);
      //recursively call Combi() with incremented value of ‘currLen’ and ‘s’.
   check[s] = false;
   Combi(a, reqLen, s + 1, currLen, check, l);
      // recursively call Combi() with only incremented value of ‘s’.
}
int main() {
   int i,n;
   bool check[n];
   cout<<"Enter the number of element array have: ";
   cin>>n;
   char a[n];
   cout<<"\n";
   for(i = 0; i < n; i++) {
      cout<<"Enter "<<i+1<<" element: ";
      cin>>a[i];
      check[i] = false;
   }
   for(i = 1; i <= n; i++) {
      cout<<"\nThe all possible combination of length "<<i<<" for the given array set:\n";
      Combi(a, i, 0, 0, check, n);
   }
   return 0;
}

Output

Enter the number of element array have: 4
Enter 1 element: 4
Enter 2 element: 3
Enter 3 element: 2
Enter 4 element: 1
The all possible combination of length 1 for the given array set:
4
3
2
1
The all possible combination of length 2 for the given array set:
4 3
4 2
4 1
3 2
3 1
2 1
The all possible combination of length 3 for the given array set:
4 3 2
4 3 1
4 2 1
3 2 1
The all possible combination of length 4 for the given array set:
4 3 2 1