DSA — Selection Sort

What is Selection Sort?

Finds the minimum element and places it at the beginning, repeating for each position.

def selection_sort(arr):
    n = len(arr)
    for i in range(n):
        min_idx = i
        for j in range(i+1, n):
            if arr[j] < arr[min_idx]:
                min_idx = j
        arr[i], arr[min_idx] = arr[min_idx], arr[i]
    return arr

How it Works

[64, 25, 12, 22, 11]
 ↓
[11, 25, 12, 22, 64]
    ↓
[11, 12, 25, 22, 64]
       ↓
[11, 12, 22, 25, 64]

Time Complexity

Case	Complexity
Best	O(n²)
Average	O(n²)
Worst	O(n²)

Characteristics

• Not stable
• In-place
• Simple to implement
• Always O(n²) comparisons

Mini Practice

1. Implement selection sort
2. Sort in descending order
3. Find number of swaps
4. Compare with bubble sort

Up Next

Continue with Insertion Sort — insertion sorting algorithm.