update 50

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_50.java

@@ -51,4 +51,24 @@ public double myPow(double x, int n) {
             return answer;
         }
     }
+
+    public static class Solution3 {
+        /**
+         * credit: https://leetcode.com/problems/powx-n/solutions/19546/short-and-easy-to-understand-solution/comments/162293
+         */
+        public double myPow(double x, int n) {
+            if (n == 0) {
+                return 1;
+            }
+            if (n < 0) {
+                //this is to avoid integer overflow
+                return 1 / x * myPow(1 / x, -(n + 1));
+            }
+            if (n % 2 == 0) {
+                return myPow(x * x, n / 2);
+            } else {
+                return x * myPow(x * x, n / 2);
+            }
+        }
+    }
 }

src/test/java/com/fishercoder/_50Test.java

@@ -9,16 +9,19 @@
 public class _50Test {
     private static _50.Solution1 solution1;
     private static _50.Solution2 solution2;
+    private static _50.Solution3 solution3;
 
     @BeforeEach
     public void setup() {
         solution1 = new _50.Solution1();
         solution2 = new _50.Solution2();
+        solution3 = new _50.Solution3();
     }
 
     @Test
     public void test1() {
         assertEquals(1024.00000, solution1.myPow(2.00000, 10), 0.00001);
         assertEquals(1024.00000, solution2.myPow(2.00000, 10), 0.00001);
+        assertEquals(1024.00000, solution3.myPow(2.00000, 10), 0.00001);
     }
 }