Pow(x, n) : Accepted

Author: gouthampradhan

README.md

@@ -32,6 +32,7 @@ My accepted leetcode solutions to some of the common interview problems.
 - [Sqrt(x)](problems/src/binary_search/SqrtX.java) (Easy)
 - [Search Insert Position](problems/src/binary_search/SearchInsertPosition.java) (Easy)
 - [Median of Two Sorted Arrays](problems/src/binary_search/MedianOfTwoSortedArrays.java) (Hard)
+- [Pow(x, n)](problems/src/binary_search/PowXN.java) (Medium)
 
 #### [Bit Manipulation](problems/src/bit_manipulation)
 

problems/src/binary_search/PowXN.java

@@ -0,0 +1,36 @@
+package binary_search;
+
+/**
+ * Created by gouthamvidyapradhan on 23/05/2017.
+
+ Implement pow(x, n).
+
+ Solution: Works with O(log n)
+ */
+public class PowXN
+{
+    /**
+     * Main method
+     * @param args
+     * @throws Exception
+     */
+    public static void main(String[] args) throws Exception
+    {
+        System.out.println(1 / new PowXN().myPow(2.00000, -2147483648));
+    }
+
+    public double myPow(double x, int n)
+    {
+        if(n == 0) return 1D;
+        long N = n; //use long to avoid overflow.
+        return solve(n < 0 ? (1 / x) : x, N < 0 ? (N * -1) : N);
+    }
+
+    public double solve(double x, long n)
+    {
+        if(n == 1) return x;
+        double val = solve(x, n / 2);
+        return val * val * ((n % 2) == 0 ? 1 : x);
+    }
+
+}