refactor 89

fishercoder1534 · fishercoder1534 · commit 19b4c0b71a32 · 2019-05-18T17:17:44.000-07:00
diff --git a/src/main/java/com/fishercoder/solutions/_89.java b/src/main/java/com/fishercoder/solutions/_89.java
@@ -39,4 +39,31 @@ public List<Integer> grayCode(int n) {
     }
   }
 
+  public static class Solution2 {
+    public List<Integer> grayCode(int n) {
+      List<Integer> result = new ArrayList();
+      for (int i = 0; i < Math.pow(2, n); i++) {
+        result.add(i ^ (i >> 1));
+      }
+      return result;
+    }
+  }
+
+  public static void main (String... args) {
+    System.out.println("-----------------------------------------------------------------------------------------");
+    System.out.println("How to understand i << n? It means n to the power of two, see below. So we have an equivalent solution, which is solution2.");
+    System.out.println("1 << 2: " +  (1 << 2));
+    System.out.println("1 << 3: " +  (1 << 3));
+    System.out.println("1 << 4: " +  (1 << 4));
+    System.out.println("1 << 5: " +  (1 << 5));
+    System.out.println("1 << 6: " +  (1 << 6));
+    System.out.println("-----------------------------------------------------------------------------------------");
+    System.out.println("How to understand i >> 1? It means to shift the number i to the right by 1 bit, see below");
+    System.out.println("2 >> 1: " +  (2 >> 1));
+    System.out.println("3 >> 1: " +  (3 >> 1));
+    System.out.println("4 >> 1: " +  (4 >> 1));
+    System.out.println("5 >> 1: " +  (5 >> 1));
+    System.out.println("6 >> 1: " +  (6 >> 1));
+  }
+
 }
diff --git a/src/test/java/com/fishercoder/_89Test.java b/src/test/java/com/fishercoder/_89Test.java
@@ -10,14 +10,17 @@
 public class _89Test {
 
   private static _89.Solution1 solution1;
+  private static _89.Solution2 solution2;
 
   @BeforeClass
   public static void setup() {
     solution1 = new _89.Solution1();
+    solution2 = new _89.Solution2();
   }
 
   @Test
   public void test1() {
     assertEquals(Arrays.asList(0, 1, 3, 2, 6, 7, 5, 4), solution1.grayCode(3));
+    assertEquals(Arrays.asList(0, 1, 3, 2, 6, 7, 5, 4), solution2.grayCode(3));
   }
 }

Original file line number	Diff line number	Diff line change
`@@ -10,14 +10,17 @@`
`10`	`10`	`public class _89Test {`
`11`	`11`
`12`	`12`	`private static _89.Solution1 solution1;`
	`13`	`+ private static _89.Solution2 solution2;`
`13`	`14`
`14`	`15`	`@BeforeClass`
`15`	`16`	`public static void setup() {`
`16`	`17`	`solution1 = new _89.Solution1();`
	`18`	`+ solution2 = new _89.Solution2();`
`17`	`19`	`}`
`18`	`20`
`19`	`21`	`@Test`
`20`	`22`	`public void test1() {`
`21`	`23`	`assertEquals(Arrays.asList(0, 1, 3, 2, 6, 7, 5, 4), solution1.grayCode(3));`
	`24`	`+ assertEquals(Arrays.asList(0, 1, 3, 2, 6, 7, 5, 4), solution2.grayCode(3));`
`22`	`25`	`}`
`23`	`26`	`}`