CODEWITHSUNDEEP
c++creturnoutputgeneric-programming
Rohit Sthapit
Rohit Sthapit

Reputation: 85

What is the following function returning ?

int fn(unsigned int x)
{
int count = 0 ;
for(; x!=0; x&=(x-1))
    count ++;
return count;
}

I tried it out in the complier but couldn't figure out what is happening. I think it's something to do with the number of bits the in x, but what?

Upvotes: 2

Views: 163

Answers (2)

Mani
Mani

Reputation: 17585

I explain what you have done :)

As per your code , following will happen if x = 5

1) In first iteration of loop,

  a) condition check : .... 0101(X) ! = 0 ,
  b) body : count will be 1 ;
  c) increment part : .... 0101 &= .... 0100 => .... 0100

2) In second Itearation

a) condition check : .... 0100(X) ! = 0 ,
  b) body : count will be 2 ;
  c) increment part : .... 0100 &= .... 0011 => .... 0000

The count is equal to 2 which is number of bits set in X(5)

Upvotes: 0

Drew Dormann
Drew Dormann

Reputation: 63775

It's a bit trick. :)

You're returning the number of bits set to 1.

Upvotes: 9

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