Selection Sort — VizionX (CTC)

Selection Sort is a simple comparison-based sorting algorithm. It divides the input list into two parts: the sorted part at the front and the unsorted part at the back. On each pass, it selects the smallest (or largest) element from the unsorted part and swaps it with the first unsorted element, growing the sorted part by one.

Selection Sort is easy to understand and implement, but it is not adaptive and always performs the same number of comparisons, regardless of the initial order of the list. It is generally slower than more advanced algorithms for large datasets.

Its main advantage is simplicity and minimal memory usage, as it only requires a constant amount of additional space.

Time Complexity

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

Code Examples

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# Python - selection sort
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

// C++ - selection sort
#include <vector>
using namespace std;

void selectionSort(vector<int>& arr) {
    int n = arr.size();
    for (int i = 0; i < n; i++) {
        int min_idx = i;
        for (int j = i+1; j < n; j++) {
            if (arr[j] < arr[min_idx]) {
                min_idx = j;
            }
        }
        swap(arr[i], arr[min_idx]);
    }
}

// Java - selection sort
public class SelectionSort {
    public static void selectionSort(int[] arr) {
        int n = arr.length;
        for (int i = 0; i < n; i++) {
            int min_idx = i;
            for (int j = i+1; j < n; j++) {
                if (arr[j] < arr[min_idx]) {
                    min_idx = j;
                }
            }
            int temp = arr[i];
            arr[i] = arr[min_idx];
            arr[min_idx] = temp;
        }
    }
}

// JavaScript - selection sort
function selectionSort(arr) {
  const n = arr.length;
  for (let i = 0; i < n; i++) {
    let min_idx = i;
    for (let j = i + 1; j < n; j++) {
      if (arr[j] < arr[min_idx]) {
        min_idx = j;
      }
    }
    [arr[i], arr[min_idx]] = [arr[min_idx], arr[i]];
  }
  return arr;
}