Selection Sort Explained Simply — Algorithm, Code & Complexity

Selection Sort's superpower: fewest swaps of any simple sorting algorithm — at most n-1 total. In systems where writes are expensive, this matters.

🧠 The Core Idea

Every pass: scan the unsorted region, find the minimum, swap it to the front.

Analogy: Sorting 30 answer sheets by roll number. Scan all, find Roll No. 1, pull it. Scan remaining, find Roll No. 2. Repeat.

📋 Example: [64, 25, 12, 22, 11]

Pass	Min	Result
1	11	[11, 25, 12, 22, 64]
2	12	[11, 12, 25, 22, 64]
3	22	[11, 12, 22, 25, 64]
4	25	[11, 12, 22, 25, 64] ✅

5 elements → 4 passes → only 2 actual swaps.

💻 JavaScript

function selectionSort(arr) {
  const n = arr.length;
  for (let i = 0; i < n - 1; i++) {
    let minIdx = i;
    for (let j = i + 1; j < n; j++) {
      if (arr[j] < arr[minIdx]) minIdx = j;
    }
    if (minIdx !== i) [arr[i], arr[minIdx]] = [arr[minIdx], arr[i]];
  }
  return arr;
}

⏱ Complexity

Case	Time	Space	Stable	Max Swaps
All cases	O(n²)	O(1)	❌	n-1

🆚 vs Bubble Sort

Factor	Selection	Bubble
Swaps	n-1 max ✅	Up to n²/2 ❌
Stable	❌ No	✅ Yes

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Part 8 of the Bitveen DSA Series. Originally published at bitveen.com