🌟 Selection Sort 

Selection Sort is a simple sorting algorithm.
It works by repeatedly finding the minimum (or maximum) element from the unsorted part of the array and moving it to the beginning.

✏️ How Selection Sort works step-by-step:

• Start with the first element of the array.

• Find the smallest element in the array.

• Swap it with the first element.

• Move to the second position, and repeat the process for the remaining elements.

• Continue until the entire array is sorted.

---

Selection Sort Algorithm

Input: An array arr[] of size n
Output: Sorted array in ascending order

for i = 0 to i< n-1 do
    min_index = i
    for j = i+1 to i < n-1 do
        if arr[j] < arr[min_index] then
            min_index = j
    if min_index ≠ i then
        swap arr[i] and arr[min_index]

---

🔥 Let's Break it Down:

• Outer loop (i): For each position in the array.

• Inner loop (j): Find the smallest element in the unsorted part.

• Swap the smallest found with the current ith element.

---

📜 Simple Example

Suppose the array is:
arr = [64, 25, 12, 22, 11]

Steps:

1. Find the minimum from index 0 to 4 → 11 → Swap 11 and 64 → [11, 25, 12, 22, 64]

2. Find the minimum from index 1 to 4 → 12 → Swap 12 and 25 → [11, 12, 25, 22, 64]

3. Find the minimum from index 2 to 4 → 22 → Swap 22 and 25 → [11, 12, 22, 25, 64]

4. Find the minimum from index 3 to 4 → 25 already minimum → No swap

5. Last element is automatically sorted.

Final sorted array: [11, 12, 22, 25, 64]

---

✅ Key Points

• Time Complexity:

  • Best Case: O(n²)

  • Average Case: O(n²)

  • Worst Case: O(n²)

• Space Complexity: O(1) (In-place sorting)

• Stability: ❌ Not stable (unless modified carefully)

• Useful: When memory is very limited.

C Program Selection Sort

#include <stdio.h>

// Function to perform Selection Sort

void selectionSort(int arr[], int n) {

    int i, j, min_idx, temp;

    

    for (i = 0; i < n-1; i++) {

        min_idx = i;

        // Find the minimum element in the unsorted part

        for (j = i+1; j < n; j++) {

            if (arr[j] < arr[min_idx])

                min_idx = j;

        }

        // Swap the found minimum with the first element

        if (min_idx != i) {

            temp = arr[i];

            arr[i] = arr[min_idx];

            arr[min_idx] = temp;

        }

    }

}

void printArray(int arr[], int n) {

    for (int i=0; i<n; i++)

        printf("%d ", arr[i]);

    printf("\n");

}

void readArray(int arr[], int n) {

    for (int i=0; i<n; i++)

        scanf("%d", &arr[i]);

    

}

int main() {

    int arr[50] ;

    int n;

    

    printf("Enter the number of elements \n");

    scanf("%d",&n);

    printf("Enter the array elements\n");

    readArray(arr,n);

    

    printf("Original array: ");

    printArray(arr, n);

    selectionSort(arr, n);

    printf("Sorted array: ");

    printArray(arr, n);

    return 0;

}

Output

Enter the number of elements 

5

Enter the array elements

6 3 9 1 2

Original array: 6 3 9 1 2 

Sorted array: 1 2 3 6 9