**Objective: **Given a binary tree, write a non recursive or iterative algorithm for preorder traversal**.**

Tree Traversals — Preorder

**Example:**

Earlier we have seen “**What is preorder traversal and recursive algorithm for it**”, In this article we will solve it with iterative/Non Recursive manner.

Since we are not using recursion, we will use the **Stack** to store the traversal, we need to remember that preorder traversal is, first traverse the root node then left node followed by the right node.

**Pseudo Code:**

- Create a Stack.
- Print the root and push it to Stack and go left i.e root=root.left and till it hits the NULL.
- If root is null and Stack is empty Then
- return, we are done.

- Else
- Pop the top Node from the Stack and set it as, root = popped_Node.
- Go right, root = root.right.
- Go to step 2.

- End If

See the animated image below and code for more understanding.

Preorder traversal

**Complete Code:**

**Output:**

1 2 4 5 3 6 7
1 2 4 5 3 6 7

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