Implementation

Let’s code selection sort. It’s straightforward to implement.

Basic Implementation

              function selectionSort(arr) {
const n = arr.length;

for (let i = 0; i < n - 1; i++) {
  let minIndex = i;
  
  // Find minimum in unsorted portion
  for (let j = i + 1; j < n; j++) {
    if (arr[j] < arr[minIndex]) {
      minIndex = j;
    }
  }
  
  // Swap if minimum is not at i
  if (minIndex !== i) {
    [arr[i], arr[minIndex]] = [arr[minIndex], arr[i]];
  }
}

return arr;
}
            

              def selection_sort(arr):
  n = len(arr)
  
  for i in range(n - 1):
      min_index = i
      
      # Find minimum in unsorted portion
      for j in range(i + 1, n):
          if arr[j] < arr[min_index]:
              min_index = j
      
      # Swap if minimum is not at i
      if min_index != i:
          arr[i], arr[min_index] = arr[min_index], arr[i]
  
  return arr
            

Try It Yourself

Code Explanation

1. Outer loop (i): Runs n-1 times

   • After each iteration, one element is in place

2. Find minimum: Inner loop finds minimum

   • Starts from i+1 (unsorted portion)
   • Updates minIndex when smaller element found

3. Swap: Places minimum at correct position

   • Only swaps if minimum is not already at i

Edge Cases

• Empty array: Returns empty array (loops don’t run)
• Single element: Already sorted, returns as-is
• Already sorted: Still runs all passes (inefficient)
• All same values: No swaps needed, but still runs

What’s Next?

Now that you can implement it, let’s analyze its performance and complexity.