Day-46 Implementation of pow(x,y)

Author: mandliya

README.md

@@ -4,9 +4,9 @@
 
 | Current Status|     Stats     |
 | :------------: | :----------: |
-| Total Problems | 64 |
-| Current Streak | 45 |
-| Longest Streak | 45 ( August 17, 2015 - September 30, 2015 ) |
+| Total Problems | 65 |
+| Current Streak | 46 |
+| Longest Streak | 46 ( August 17, 2015 - October 1, 2015 ) |
 
 </center>
 
@@ -105,6 +105,7 @@ Include contains single header implementation of data structures and some algori
 | :------------ | :----------: |
 |  Print all the permutations of a string. Example: Permutations of ABC are ABC, ACB, BCA, BAC, CAB, CBA | [string_permutations.cpp] (math_problems/string_permutations.cpp) |
 | Euclidean algorithm to find greatest common divisor of two numbers. (Iterative and recursive)|[gcd.cpp](math_problems/gcd.cpp)|
+| Implement pow(x,y) using divide and conquer approach. Try implementing it in O(logn)| [pow.cpp](math_problems/pow.cpp)|
 
 ### Stack Problems
 | Problem | Solution |

math_problems/pow.cpp

@@ -0,0 +1,38 @@
+/*
+ *  A simple divide and conquer approach to calculate pow(x,y)
+ */
+
+#include <iostream>
+
+
+double pow( double x, int y )
+{
+	//base case
+	if ( y == 0 ) {
+		return 1;
+	}
+	double temp = pow(x, y/2);
+	if ( y % 2 == 0 ) {
+		return temp * temp;
+	} else {
+		if ( y > 0 ) {
+			return x * temp * temp;
+		} else {
+			return ( temp * temp ) / x;
+		}
+	}
+}
+
+int main()
+{
+	std::cout << "Program to calculate power y to the base x\n";
+	double x;
+	int y;
+	std::cout << "Enter base : ";
+	std::cin >> x;
+	std::cout << "Enter power(int + or -) : ";
+	std::cin >> y;
+	std::cout << "Power " << y << " to the base " << x << " is: ";
+	std::cout <<  pow(x, y) << std::endl;
+	return 0;
+}