What is meaning of following code?

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int printSubset(char *set,int &elements)
{
	int total_subsets = pow(2,elements);
	cout<<"\n Total subset are = 2^"<< elements <<" = "<< total_subsets <<endl;
	cout<<"\nEmpty set";
    
    for(int c=0; c<total_subsets; c++)
    {
      for(int j=0; j<elements; j++)
       {
		if(c&(1<<j))
          {
          	 cout<< set[j];
          }          
	  }
	  cout<<"\n\n";
    }
}

What I have tried:

Actually this code is for making subsets of a set
But i dont understand the following code that how does it works

Especially the
if condition so please tell me about the condition.

for(int c=0; c<total_subsets; c++)
{
  for(int j=0; j<elements; j++)
   {
if(c&(1<<j))
      {
         cout<< set[j];
      }
   }
  cout<<"\n\n";
}

Posted 21-Jun-18 18:18pm

Member 13881359

Updated 21-Jun-18 18:59pm

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OriginalGriff · Answer 1 · 2018-06-21T19:00:00

When you don't understand a bit of code, look at it and dissect it into it's component parts.

C++

if(c&(1<<j))

Breaks down into

C++

if (...)

and

C++

c&(1<<j)

The first part I know you understand - it's a normal if, and the second part is the condition which evaluates to true or false.

C++

c & (1 << j)

;Is also in two parts:

C++

c & ...

And

C++

1 << j

The first part is a binary AND of the two values: c and the second part, and a binary AND is simple: for each bit in the inputs, the resulting bit is 1 if and only if both the input bits are 1. Otherwise it's a 0. (Interesting Facts about Bitwise Operators in C - GeeksforGeeks[<a href="https://www.geeksforgeeks.org/interesting-facts-bitwise-operators-c/" target="_blank" title="New Window>^] should help)
The second part is also simple: it's a 1 shifted j places to the right (the link above also explains this). So if j is 0 then it results in 1, for j == 1 it results in 2, for j = 2 it gives 4, and so on.

So the whole if is checking for a 1 bit in a specific position in c

This is all in the documentation: Operators in C / C++ - GeeksforGeeks[^]