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Semester 2/Programming 2/Week 10 Revision/Q5.md

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+a) List the order in which the nodes are visited in: 
+post-order.
+![](Pasted%20image%2020240319225420.png)
+D,B,F,G,E,C,A
+
+pre-order
+A,B,D,C,E,F,G
+
+in-order
+D,B,F,E,G,C,A
+
+b)
+```java
+public class BinTreeNode
+{
+	public String info;
+	public BinTreeNode leftChild, rightChild;
+}
+```
+
+```java
+public void postTraverse( BinTreeNode node )
+{
+	if ( node != null )
+	{
+		postTraverse( node.leftNode );
+		postTraverse( node.rightNode );
+		System.out.println( node.info );
+	}
+}
+```
+
+c) The following method counts the number of nodes in the tree
+```java
+public int countTree(BinTreeNode t)
+{
+	int count;
+	if (t == null)
+		count = 0
+	else
+		count = countTree(t.leftChild)+countTree(t.rightChild)+1;
+	return count;
+}
+```
+![](Pasted%20image%2020240319234142.png)
+
+countTree(root)
+-> count = countTree(t.leftChild) + countTree(t.rightChild+1)
+countTree(t.leftChild)
+-> return 1, since left and right child null
+countTree(t.rightChild)
+-> return 1, since left and right child null
+count = 1 + 1 + 1 = 3