Create power_of_two.cpp (#1315)

* Create power_of_two.cpp

This Pull Request is for HacktoberFest 2020

* Update math/power_of_two.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update math/power_of_two.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update math/power_of_two.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update math/power_of_two.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update math/power_of_two.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update math/power_of_two.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* updating DIRECTORY.md

* clang-format and clang-tidy fixes for 3d017c44

* Update math/power_of_two.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update math/power_of_two.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update math/power_of_two.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* clang-format and clang-tidy fixes for f76c1009

Co-authored-by: David Leal <halfpacho@gmail.com>
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

DIRECTORY.md

@@ -164,6 +164,7 @@
   * [Ncr Modulo P](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/ncr_modulo_p.cpp)
   * [Number Of Positive Divisors](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/number_of_positive_divisors.cpp)
   * [Power For Huge Numbers](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/power_for_huge_numbers.cpp)
+  * [Power Of Two](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/power_of_two.cpp)
   * [Prime Factorization](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/prime_factorization.cpp)
   * [Prime Numbers](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/prime_numbers.cpp)
   * [Primes Up To Billion](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/primes_up_to_billion.cpp)

math/power_of_two.cpp

@@ -0,0 +1,66 @@
+/**
+ * @file
+ * @brief Implementation to check whether a number is a power of 2 or not.
+ *
+ * @details
+ * This algorithm uses bit manipulation to check if a number is a power of 2 or
+ * not.
+ *
+ * ### Algorithm
+ * Let the input number be n, then the bitwise and between n and n-1 will let us
+ * know whether the number is power of 2 or not
+ *
+ * For Example,
+ * If N= 32 then N-1 is 31, if we perform bitwise and of these two numbers then
+ * the result will be zero, which indicates that it is the power of 2
+ * If N=23 then N-1 is 22, if we perform bitwise and of these two numbers then
+ * the result will not be zero , which indicates that it is not the power of 2
+ * \note This implementation is better than naive recursive or iterative
+ * approach.
+ *
+ * @author [Neha Hasija](https://github.com/neha-hasija17)
+ */
+
+#include <iostream>  /// for std::cout
+
+/**
+ * @namespace math
+ * @brief Mathematical algorithms
+ */
+namespace math {
+/**
+ * @brief Function to test above algorithm
+ * @param n description
+ * @returns void
+ */
+void power_of_two(int n) {
+    /**
+     * This function finds whether a number is power of 2 or not
+     * @param n value for which we want to check
+     * prints the result, as "Yes, the number n is a power of 2" or
+     * "No, the number is not a power of 2" without quotes
+     */
+    /// result stores the
+    /// bitwise and of n and n-1
+    int result = n & (n - 1);
+    if (result == 0) {
+        std::cout << "Yes, the number " << n << " is a power of 2";
+    } else {
+        std::cout << "No, the number " << n << " is not a power of 2";
+    }
+}
+}  // namespace math
+
+/**
+ * @brief Main function
+ * @returns 0 on exit
+ */
+int main() {
+    int n = 0;
+    /// n stores the input from the user
+    std::cout << "enter a number " << std::endl;
+    std::cin >> n;
+    /// function call with @param n
+    math::power_of_two(n);
+    return 0;
+}