Create power_of_two.cpp

This Pull Request is for HacktoberFest 2020

math/power_of_two.cpp

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+
+/**
+ * @file power_of_two.cpp
+ * @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>
+/**
+ * Function to test above algorithm
+ */
+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";
+             
+}
+
+/** Driver Code */
+/**
+ * @brief Main function
+ * @returns 0 on exit
+ */
+int main() {
+    int n;
+    ///n stores the input from the user
+    std::cout<<"enter a number "<<std::endl;
+    std::cin>>n;
+    ///function call with @param n
+    power_of_two(n);
+    return 0;
+}