# 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

karthikeya Boyini

I love programming (: That's all I know

Updated on: 30-Jul-2019

1K+ Views

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