wrong output on printing subsets of array

Question

I am trying to print all the subsets of an array. But not getting the correct output.

#include<iostream>
using namespace std;

int arr[]={1,2,3,4,5};
int n=5;

void print(int a[],int cnt, int idx)
{
    if(idx==n)
    {
        for(int i=0;i<cnt;i++)
        {
            cout<<a[i]<<" ";
        }
        cout<<endl;
        return;
    }
    a[cnt]=arr[idx];
    print(a,cnt,idx+1);
    print(a,cnt+1,idx+1);
}
int main()
{
    int a[5]={0};
    print(a,0,0);
}

the above code only prints "5" Please help me to rectify the same.

A `print` function typically does not modify the thing it is printing. What is the purpose of modifying `a` in your print function? — Drew Dormann, Mar 08 '21 at 15:47
You might be interested by [Powerset section of my answer](https://stackoverflow.com/a/25556248/2684539). — Jarod42, Mar 08 '21 at 15:50

score 2 · Accepted Answer · answered Mar 08 '21 at 16:00

Replace the array with a vector. As the array in C++ is passed by reference, the print function is accessing the same array, which causes the problem.

#include <iostream>
#include<vector>
using namespace std;
int arr[]={1,2,3,4,5};
int n=5;

void print(vector<int>a,int cnt, int idx)
{
    if(idx==n)
    {
        for(int i=0;i<cnt;i++)
        {
            cout<<a[i]<<" ";
        }
        cout<<endl;
        return;
    }
    a[cnt]=arr[idx];
    print(a,cnt,idx+1);
    print(a,cnt+1,idx+1);
}
int main()
{
    vector<int >a(5,0);
    print(a,0,0);
}

wrong output on printing subsets of array

1 Answers1