## DSA Tutorial

DSA HOME DSA Intro DSA Simple Algorithm

## Arrays

DSA Arrays DSA Bubble Sort DSA Selection Sort DSA Insertion Sort DSA Quick Sort DSA Counting Sort DSA Radix Sort DSA Merge Sort DSA Linear Search DSA Binary Search

## Stacks & Queues

DSA Stacks DSA Queues

## Hash Tables

DSA Hash Tables DSA Hash Sets DSA Hash Maps

## Trees

DSA Trees DSA Binary Trees DSA Pre-order Traversal DSA In-order Traversal DSA Post-order Traversal DSA Array Implementation DSA Binary Search Trees DSA AVL Trees

## Graphs

DSA Graphs Graphs Implementation DSA Graphs Traversal DSA Cycle Detection

## Shortest Path

DSA Shortest Path DSA Dijkstra's DSA Bellman-Ford

## Minimum Spanning Tree

Minimum Spanning Tree DSA Prim's DSA Kruskal's

## Maximum Flow

DSA Maximum Flow DSA Ford-Fulkerson DSA Edmonds-Karp

## Time Complexity

Introduction Bubble Sort Selection Sort Insertion Sort Quick Sort Counting Sort Radix Sort Merge Sort Linear Search Binary Search

## DSA Reference

DSA Euclidean Algorithm DSA Huffman Coding DSA The Traveling Salesman DSA 0/1 Knapsack DSA Memoization DSA Tabulation DSA Dynamic Programming DSA Greedy Algorithms

## DSA Examples

DSA Examples DSA Exercises DSA Quiz DSA Certificate

# DSA In-order Traversal

## In-order Traversal of Binary Trees

In-order Traversal is a type of Depth First Search, where each node is visited in a certain order. Read more about Binary Tree traversals in general here.

Run the animation below to see how an In-order Traversal of a Binary Tree is done.

Result:

In-order Traversal does a recursive In-order Traversal of the left subtree, visits the root node, and finally, does a recursive In-order Traversal of the right subtree. This traversal is mainly used for Binary Search Trees where it returns values in ascending order.

What makes this traversal "in" order, is that the node is visited in between the recursive function calls. The node is visited after the In-order Traversal of the left subtree, and before the In-order Traversal of the right subtree.

This is how the code for In-order Traversal looks like:

### Example

Python:

def inOrderTraversal(node):
if node is None:
return
inOrderTraversal(node.left)
print(node.data, end=", ")
inOrderTraversal(node.right)
Run Example ยป

The inOrderTraversal() function keeps calling itself with the current left child node as an argument (line 4) until that argument is None and the function returns (line 2-3).

The first time the argument node is None is when the left child of node C is given as an argument (C has no left child).

After that, the data part of node C is printed (line 5), which means that 'C' is the first thing that gets printed.

Then, node C's right child is given as an argument (line 6), which is None, so the function call returns without doing anything else.

After 'C' is printed, the previous inOrderTraversal() function calls continue to run, so that 'A' gets printed, then 'D', then 'R', and so on.

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