gray code

Author: xiaoningning

PuzzleCoding/src/GrayCode.java

@@ -0,0 +1,57 @@
+/**
+ * Created with IntelliJ IDEA.
+ * Print the N-bit binary reflected Gray code using recursion.
+ * <p/>
+ * Gray Code of 3:
+ * 000
+ * 001
+ * 011
+ * 010
+ * 110
+ * 111
+ * 101
+ * 100
+ */
+public class GrayCode {
+    public static void main(String[] args) {
+        int N = 3;
+        grayCode(N, new boolean[N]);
+    }
+
+    public static void grayCode(int n, boolean[] show) {
+        if (n == 0) {
+            showCode(show);
+        } else {
+            show[n - 1] = false;
+            grayCode(n - 1, show);
+            show[n - 1] = true;
+            yargCode(n - 1, show);
+        }
+
+    }
+
+    // append reverse of order n gray code
+    public static void yargCode(int n, boolean[] show) {
+        if (n == 0) {
+            showCode(show);
+        } else {
+            show[n - 1] = true;
+            grayCode(n - 1, show);
+            show[n - 1] = false;
+            yargCode(n - 1, show);
+        }
+    }
+
+    public static void showCode(boolean[] show) {
+        String code = "";
+        for (boolean yes : show) {
+            if (yes)
+                code = "1" + code;
+            else
+                code = "0" + code;
+        }
+        System.out.println(code);
+        // System.out.println(Integer.parseInt(code, 2));
+    }
+
+}

allSubsets/src/allSubsets.java

@@ -3,7 +3,7 @@
 
 public class allSubsets{
     public static void main(String[] args){
-        int[] a = {1,2,3,4};
+        int[] a = {1,2,3};
         ArrayList<ArrayList<Integer>> allsubsets = new ArrayList<ArrayList<Integer>>();
         System.out.println("take subset:");
         allsubsets = genSubsets(a, 0);