count_of_set_bits.cpp File Reference

Implementation to count number of set bits of a number in an integer. More...

#include <cassert>
#include <iostream>

Include dependency graph for count_of_set_bits.cpp:

Namespaces
namespace	bit_manipulation
	for IO operations
namespace	count_of_set_bits
	Functions for the count sets bits implementation.

Functions
std::uint64_t	bit_manipulation::count_of_set_bits::countSetBits (std ::int64_t n)
	The main function implements set bit count. More...
static void	test ()
int	main ()
	Main function. More...

Detailed Description

Implementation to count number of set bits of a number in an integer.

We are given an integer number. We need to calculate the number of set bits in it.

A binary number consists of two digits. They are 0 & 1. Digit 1 is known as set bit in computer terms. Worst Case Time Complexity: O(log n) Space complexity: O(1)

Author

Swastika Gupta

Prashant Thakur

Function Documentation

countSetBits()

std::uint64_t bit_manipulation::count_of_set_bits::countSetBits

(

std ::int64_t

n

)

The main function implements set bit count.

Parameters

n	is the number whose set bit will be counted

Returns

total number of set-bits in the binary representation of number n

                                         { // int64_t is preferred over int so that
                                          // no Overflow can be there.
 
    int count = 0; // "count" variable is used to count number of set-bits('1') in
                   // binary representation of number 'n'
    while (n != 0)
    {
        ++count;
        n = (n & (n - 1));
    }
    return count;
    // Why this algorithm is better than the standard one?
    // Because this algorithm runs the same number of times as the number of
    // set-bits in it. Means if my number is having "3" set bits, then this while loop
    // will run only "3" times!!
}

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main()

int main

(

void

)

Main function.

Returns

0 on exit

           {
    test();  // run self-test implementations
    return 0;
}

test()

static void test ( )

static

                   {
    // n = 4 return 1
    assert(bit_manipulation::count_of_set_bits::countSetBits(4) == 1);
    // n = 6 return 2
    assert(bit_manipulation::count_of_set_bits::countSetBits(6) == 2);
    // n = 13 return 3
    assert(bit_manipulation::count_of_set_bits::countSetBits(13) == 3);
    // n = 9 return 2
    assert(bit_manipulation::count_of_set_bits::countSetBits(9) == 2);
    // n = 15 return 4
    assert(bit_manipulation::count_of_set_bits::countSetBits(15) == 4);
    // n = 25 return 3
    assert(bit_manipulation::count_of_set_bits::countSetBits(25) == 3);
    // n = 97 return 3
    assert(bit_manipulation::count_of_set_bits::countSetBits(97) == 3);
    // n = 31 return 5
    assert(bit_manipulation::count_of_set_bits::countSetBits(31) == 5);
    std::cout << "All test cases successfully passed!" << std::endl;
}