make Nary tree from its pre and post order

Author: dheeraj9198

src/BinaryTree/CheckIfHeightBalancedBt.java

@@ -6,7 +6,7 @@
  */
 public class CheckIfHeightBalancedBt {
 
-    static class Data{
+    static class Data {
         private int height;
         private boolean balanced;
 
@@ -16,20 +16,17 @@ public Data(int height, boolean balanced) {
         }
     }
 
-    private static Data checkIfHeightBalanced(Node node){
-           if(node == null){
-               return new Data(0,true);
-           }else if(node.left == null && node.right == null){
-               return new Data(1,true);
-           }
-
+    private static Data checkIfHeightBalanced(Node node) {
+        if (node == null) {
+            return new Data(0, true);
+        }
         Data leftData = checkIfHeightBalanced(node.left);
         Data rightData = checkIfHeightBalanced(node.right);
 
-        if(leftData.balanced && rightData.balanced && Math.abs(leftData.height - rightData.height) <=1){
-                 return new Data(Math.max(leftData.height,rightData.height)+1,true);
+        if (leftData.balanced && rightData.balanced && Math.abs(leftData.height - rightData.height) <= 1) {
+            return new Data(Math.max(leftData.height, rightData.height) + 1, true);
         }
-        return new Data(0,false);
+        return new Data(0, false);
     }
 
     public static void main(String[] strings) {
@@ -39,13 +36,13 @@ public static void main(String[] strings) {
         root.right = new Node(3);
 
         root.left.left = new Node(7);
-
         root.left.right = new Node(6);
+
         root.right.left = new Node(5);
         root.right.right = new Node(4);
 
         root.left.left.left = new Node(9);
-        root.left.left.left.left = new Node(999);
+        /*root.left.left.left.left = new Node(999);*/
 
 
         System.out.println(checkIfHeightBalanced(root).balanced);

src/BinaryTree/MakeNaryTreeFromPrePost.java

@@ -0,0 +1,72 @@
+package BinaryTree;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+
+/**
+ * Created by dheeraj on 7/10/2016.
+ */
+public class MakeNaryTreeFromPrePost {
+
+    static class Node {
+        int data;
+        ArrayList<Node> children;
+
+        public Node(int data) {
+            this.data = data;
+            children = new ArrayList<Node>();
+        }
+
+        @Override
+        public String toString() {
+            return data + " ";
+        }
+    }
+
+    static int[] pre = new int[]{1, 2, 3, 4, 5, 6, 7, 8, 9};
+    static int[] post = new int[]{3, 4, 2, 6, 5, 9, 8, 7, 1};
+
+    static HashSet<Integer> integerHashSet = new HashSet<>();
+
+    private static Node makeTree(int postStart, int postEnd, int preIndex) {
+        if (postEnd < postStart) {
+            return null;
+        }
+        Node node = new Node(pre[preIndex]);
+        integerHashSet.add(pre[preIndex]);
+        for (int x1 = 0; x1 < pre.length; x1++) {
+            if (!integerHashSet.contains(pre[x1])) {
+
+                int postIndex = -1;
+                for(int k =postStart;k<=postEnd;k++){
+                      if(post[k] == pre[x1]){
+                          postIndex = k;
+                          break;
+                      }
+                }
+                int ps = -1, pe = -1;
+                for (int x = postStart; x <= postIndex; x++) {
+                    if (!integerHashSet.contains(post[x])) {
+                        if (ps == -1) {
+                            ps = x;
+                            pe = x;
+                        } else {
+                            pe = x;
+                        }
+                    }
+                }
+                if (pe != -1 && ps != -1) {
+                    node.children.add(makeTree(ps, pe, x1));
+                }
+            }
+        }
+        return node;
+    }
+
+
+    public static void main(String[] strings) {
+        Node node = makeTree(0, pre.length - 1, 0);
+        System.out.println();
+    }
+
+}