Array Traversal Patterns in DSA Python

Mental Model

Go through each item in the list one by one to look at or use it.

Analogy: Like reading a book page by page from start to finish to understand the story.

Index: 0   1   2   3   4
Array: [5] -> [3] -> [8] -> [1] -> [7]

Dry Run Walkthrough

Input: array: [5, 3, 8, 1, 7], print each element

Goal: Visit every element in the array and print it in order

Step 1: Start at index 0, read value 5

Index: 0 ↑ 1   2   3   4
Array: [5] -> [3] -> [8] -> [1] -> [7]

Why: We begin at the first element to start traversal

Step 2: Move to index 1, read value 3

Index: 0   1 ↑ 2   3   4
Array: [5] -> [3] -> [8] -> [1] -> [7]

Why: Next element must be visited to continue traversal

Step 3: Move to index 2, read value 8

Index: 0   1   2 ↑ 3   4
Array: [5] -> [3] -> [8] -> [1] -> [7]

Why: Continue visiting elements in order

Step 4: Move to index 3, read value 1

Index: 0   1   2   3 ↑ 4
Array: [5] -> [3] -> [8] -> [1] -> [7]

Why: Keep moving forward to cover all elements

Step 5: Move to index 4, read value 7

Index: 0   1   2   3   4 ↑
Array: [5] -> [3] -> [8] -> [1] -> [7]

Why: Last element to visit before finishing traversal

Result:

5 -> 3 -> 8 -> 1 -> 7

Annotated Code

DSA Python

def traverse_array(arr):
    for i in range(len(arr)):
        print(arr[i], end=' -> ' if i < len(arr) - 1 else '\n')

# Driver code
array = [5, 3, 8, 1, 7]
traverse_array(array)

for i in range(len(arr)):

loop through each index from start to end to visit every element

print(arr[i], end=' -> ' if i < len(arr) - 1 else '\n')

print current element and add arrow except after last element

Output

5 -> 3 -> 8 -> 1 -> 7

Complexity Analysis

Time: O(n) because we visit each of the n elements once

Space: O(1) because we only use a few variables regardless of input size

vs Alternative: Compared to random access, traversal is simple and direct with no extra cost

Edge Cases

empty array []

No output is printed because there are no elements to visit

DSA Python

for i in range(len(arr)):

array with one element [10]

Prints the single element without arrow after it

DSA Python

print(arr[i], end=' -> ' if i < len(arr) - 1 else '\n')

When to Use This Pattern

When you need to process or check every item in a list in order, use array traversal to visit each element one by one.

Common Mistakes

Mistake: Stopping traversal early or skipping elements by wrong loop conditions
Fix: Use correct loop bounds from 0 to length-1 to cover all elements

Mistake: Printing arrow after the last element causing extra symbol
Fix: Add condition to print arrow only if not at last element

Summary

It visits each element in an array one by one in order.

Use it when you want to look at or use every item in a list.

The key is to move step-by-step from the first to the last element without skipping.