DSA — Linear Search

What is Linear Search?

Sequentially checks each element until the target is found or the list ends.

def linear_search(arr, target):
    for i in range(len(arr)):
        if arr[i] == target:
            return i
    return -1

Variations

# Find all occurrences
def find_all(arr, target):
    indices = []
    for i, val in enumerate(arr):
        if val == target:
            indices.append(i)
    return indices

# Find first occurrence
def find_first(arr, target):
    for i, val in enumerate(arr):
        if val == target:
            return i
    return -1

Time Complexity

Case	Complexity
Best	O(1)
Average	O(n)
Worst	O(n)

When to Use

• Small datasets
• Unsorted data
• Single search needed

Mini Practice

1. Implement linear search
2. Find all occurrences
3. Search in a 2D array
4. Compare with binary search

Up Next

Continue with Binary Search — efficient search algorithm.