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6272b2af08
* Modified: Replaced existing code with faster implementation * Changed long long to "int64_t" * Indentation Fixed. * Modified Documentation. * Updated authors of count_set_bits.cpp Co-authored-by: David Leal <halfpacho@gmail.com> * Apply suggestions from code review Co-authored-by: David Leal <halfpacho@gmail.com> * Added proper indentation in "main" function Co-authored-by: David Leal <halfpacho@gmail.com> Co-authored-by: David Leal <halfpacho@gmail.com>
82 lines
2.8 KiB
C++
82 lines
2.8 KiB
C++
/**
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* @file
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* @brief Implementation to [count number of set bits of a number]
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* (https://www.geeksforgeeks.org/count-set-bits-in-an-integer/) in an
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* integer.
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*
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* @details
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* We are given an integer number. We need to calculate the number of set bits in it.
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*
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* A binary number consists of two digits. They are 0 & 1. Digit 1 is known as
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* set bit in computer terms.
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* Worst Case Time Complexity: O(log n)
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* Space complexity: O(1)
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* @author [Swastika Gupta](https://github.com/Swastyy)
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* @author [Prashant Thakur](https://github.com/prashant-th18)
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*/
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#include <cassert> /// for assert
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#include <iostream> /// for IO operations
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/**
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* @namespace bit_manipulation
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* @brief Bit manipulation algorithms
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*/
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namespace bit_manipulation {
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/**
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* @namespace count_of_set_bits
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* @brief Functions for the [count sets
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* bits](https://www.geeksforgeeks.org/count-set-bits-in-an-integer/)
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* implementation
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*/
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namespace count_of_set_bits {
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/**
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* @brief The main function implements set bit count
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* @param n is the number whose set bit will be counted
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* @returns total number of set-bits in the binary representation of number `n`
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*/
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std::uint64_t countSetBits(std :: int64_t n) { // int64_t is preferred over int so that
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// no Overflow can be there.
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int count = 0; // "count" variable is used to count number of set-bits('1') in
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// binary representation of number 'n'
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while (n != 0)
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{
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++count;
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n = (n & (n - 1));
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}
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return count;
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// Why this algorithm is better than the standard one?
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// Because this algorithm runs the same number of times as the number of
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// set-bits in it. Means if my number is having "3" set bits, then this while loop
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// will run only "3" times!!
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}
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} // namespace count_of_set_bits
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} // namespace bit_manipulation
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static void test() {
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// n = 4 return 1
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assert(bit_manipulation::count_of_set_bits::countSetBits(4) == 1);
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// n = 6 return 2
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assert(bit_manipulation::count_of_set_bits::countSetBits(6) == 2);
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// n = 13 return 3
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assert(bit_manipulation::count_of_set_bits::countSetBits(13) == 3);
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// n = 9 return 2
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assert(bit_manipulation::count_of_set_bits::countSetBits(9) == 2);
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// n = 15 return 4
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assert(bit_manipulation::count_of_set_bits::countSetBits(15) == 4);
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// n = 25 return 3
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assert(bit_manipulation::count_of_set_bits::countSetBits(25) == 3);
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// n = 97 return 3
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assert(bit_manipulation::count_of_set_bits::countSetBits(97) == 3);
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// n = 31 return 5
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assert(bit_manipulation::count_of_set_bits::countSetBits(31) == 5);
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std::cout << "All test cases successfully passed!" << std::endl;
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}
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/**
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* @brief Main function
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* @returns 0 on exit
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*/
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int main() {
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test(); // run self-test implementations
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return 0;
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}
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