Create count_of_set_bits.cpp (#1515)

* Create count_of_set_bits.cpp

* Update count_of_set_bits.cpp

* updating DIRECTORY.md

* clang-format and clang-tidy fixes for d0dc7eb3

* Update bit_manipulation/count_of_set_bits.cpp

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* Update bit_manipulation/count_of_set_bits.cpp

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* Update bit_manipulation/count_of_set_bits.cpp

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* Update bit_manipulation/count_of_set_bits.cpp

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* Update bit_manipulation/count_of_set_bits.cpp

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* clang-format and clang-tidy fixes for f8606e8f

* Update bit_manipulation/count_of_set_bits.cpp

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* Update bit_manipulation/count_of_set_bits.cpp

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* Update bit_manipulation/count_of_set_bits.cpp

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* clang-format and clang-tidy fixes for 40e0f745

* Update count_of_set_bits.cpp

* Update bit_manipulation/count_of_set_bits.cpp

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* Update bit_manipulation/count_of_set_bits.cpp

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* Update bit_manipulation/count_of_set_bits.cpp

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* Update bit_manipulation/count_of_set_bits.cpp

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DIRECTORY.md

@@ -10,6 +10,7 @@
   * [Sudoku Solve](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/backtracking/sudoku_solve.cpp)
 
 ## Bit Manipulation
+  * [Count Of Set Bits](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/bit_manipulation/count_of_set_bits.cpp)
   * [Hamming Distance](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/bit_manipulation/hamming_distance.cpp)
 
 ## Ciphers

bit_manipulation/count_of_set_bits.cpp

@@ -0,0 +1,80 @@
+/**
+ * @file
+ * @brief Implementation to [count sets
+ * bits](https://www.geeksforgeeks.org/count-set-bits-in-an-integer/) in an
+ * integer.
+ *
+ * @details
+ * We are given an integer number. Let’s say, number. The task is to first
+ * calculate the binary digit of a number and then calculate the total set bits
+ * of a number.
+ *
+ * Set bits in a binary number is represented by 1. Whenever we calculate the
+ * binary number of an integer value it is formed as the combination of 0’s and
+ * 1’s. So digit 1 is known as a set bit in computer terms.
+ * Time Complexity: O(log n)
+ * Space complexity: O(1)
+ * @author [Swastika Gupta](https://github.com/Swastyy)
+ */
+
+#include <cassert>   /// for assert
+#include <iostream>  /// for io operations
+#include <vector>    /// for std::vector
+
+/**
+ * @namespace bit_manipulation
+ * @brief Bit manipulation algorithms
+ */
+namespace bit_manipulation {
+/**
+ * @namespace count_of_set_bits
+ * @brief Functions for the [count sets
+ * bits](https://www.geeksforgeeks.org/count-set-bits-in-an-integer/)
+ * implementation
+ */
+namespace count_of_set_bits {
+/**
+ * @brief The main function implements set bit count
+ * @param n is the number whose set bit will be counted
+ * @returns the count of the number set bit in the binary representation of `n`
+ */
+std::uint64_t countSetBits(int n) {
+    int count = 0;  // "count" variable is used to count number of 1's in binary
+                    // representation of the number
+    while (n != 0) {
+        count += n & 1;
+        n = n >> 1;  // n=n/2
+    }
+    return count;
+}
+}  // namespace count_of_set_bits
+}  // namespace bit_manipulation
+
+/**
+ * @brief Self-test implementations
+ * @returns void
+ */
+static void test() {
+    // 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);
+    std::cout << "All test cases successfully passed!" << std::endl;
+}
+
+/**
+ * @brief Main function
+ * @returns 0 on exit
+ */
+int main() {
+    test();  // run self-test implementations
+    return 0;
+}