Difference between Insertion sort and Selection sort

• Last Updated : 24 Jun, 2021

In this article, we will discuss the difference between the Insertion sort and the Selection sort:

Insertion sort is a simple sorting algorithm that works similar to the way you sort playing cards in your hands. The array is virtually split into a sorted and an unsorted part. Values from the unsorted part are picked and placed at the correct position in the sorted part.

Algorithm:
To sort an array of size n in ascending order:

• Iterate from arr to arr[n] over the array.
• Compare the current element (key) to its predecessor.
• If the key element is smaller than its predecessor, compare it to the elements before. Move the greater elements one position up to make space for the swapped element.

Below is the image to illustrate the Insertion Sort: Below is the program for the same:

C++

 // C++ program for the insertion sort #include using namespace std;   // Function to sort an array using // insertion sort void insertionSort(int arr[], int n) {     int i, key, j;     for (i = 1; i < n; i++) {         key = arr[i];         j = i - 1;           // Move elements of arr[0..i-1],         // that are greater than key to         // one position ahead of their         // current position         while (j >= 0 && arr[j] > key) {             arr[j + 1] = arr[j];             j = j - 1;         }         arr[j + 1] = key;     } }   // Function to print an array of size N void printArray(int arr[], int n) {     int i;       // Print the array     for (i = 0; i < n; i++) {         cout << arr[i] << " ";     }     cout << endl; }   // Driver Code int main() {     int arr[] = { 12, 11, 13, 5, 6 };     int N = sizeof(arr) / sizeof(arr);       // Function Call     insertionSort(arr, N);     printArray(arr, N);       return 0; }

Java

 // Java program for the above approach import java.util.*; class GFG {         // Function to sort an array using // insertion sort static void insertionSort(int arr[], int n) {     int i, key, j;     for (i = 1; i < n; i++)     {         key = arr[i];         j = i - 1;           // Move elements of arr[0..i-1],         // that are greater than key to         // one position ahead of their         // current position         while (j >= 0 && arr[j] > key)         {             arr[j + 1] = arr[j];             j = j - 1;         }         arr[j + 1] = key;     } }   // Function to print an array of size N static void printArray(int arr[], int n) {     int i;       // Print the array     for (i = 0; i < n; i++) {         System.out.print(arr[i] + " ");     }     System.out.println(); }     // Driver code public static void main(String[] args) {     int arr[] = { 12, 11, 13, 5, 6 };     int N = arr.length;       // Function Call     insertionSort(arr, N);     printArray(arr, N); } }   // This code is contributed by code_hunt.

Python3

 # Python 3 program for the insertion sort   # Function to sort an array using # insertion sort def insertionSort(arr, n):     i = 0     key = 0     j = 0     for i in range(1,n,1):         key = arr[i]         j = i - 1           # Move elements of arr[0..i-1],         # that are greater than key to         # one position ahead of their         # current position         while (j >= 0 and arr[j] > key):             arr[j + 1] = arr[j]             j = j - 1         arr[j + 1] = key   # Function to print an array of size N def printArray(arr, n):     i = 0       # Print the array     for i in range(n):         print(arr[i],end = " ")     print("\n",end = "")   # Driver Code if __name__ == '__main__':     arr =  [12, 11, 13, 5, 6]     N =  len(arr)       # Function Call     insertionSort(arr, N)     printArray(arr, N)           # This code is contributed by bgangwar59.

C#

 // C# program for the above approach using System; class GFG {       // Function to sort an array using     // insertion sort     static void insertionSort(int[] arr, int n)     {         int i, key, j;         for (i = 1; i < n; i++)         {             key = arr[i];             j = i - 1;               // Move elements of arr[0..i-1],             // that are greater than key to             // one position ahead of their             // current position             while (j >= 0 && arr[j] > key)             {                 arr[j + 1] = arr[j];                 j = j - 1;             }             arr[j + 1] = key;         }     }       // Function to print an array of size N     static void printArray(int[] arr, int n)     {         int i;           // Print the array         for (i = 0; i < n; i++)         {             Console.Write(arr[i] + " ");         }         Console.WriteLine();     }       // Driver code     static public void Main()     {         int[] arr = new int[] { 12, 11, 13, 5, 6 };         int N = arr.Length;           // Function Call         insertionSort(arr, N);         printArray(arr, N);     } }   // This code is contributed by Dharanendra L V

Javascript



Output:

5 6 11 12 13

The selection sort algorithm sorts an array by repeatedly finding the minimum element (considering ascending order) from the unsorted part and putting it at the beginning. The algorithm maintains two subarrays in a given array.

• The subarray is already sorted.
• Remaining subarray which is unsorted.

In every iteration of the selection sort, the minimum element (considering ascending order) from the unsorted subarray is picked and moved to the sorted subarray.

Below is the example to explains the above steps:

arr[] = 64 25 12 22 11

// Find the minimum element in arr[0...4]
// and place it at beginning
11 25 12 22 64

// Find the minimum element in arr[1...4]
// and place it at beginning of arr[1...4]
11 12 25 22 64

// Find the minimum element in arr[2...4]
// and place it at beginning of arr[2...4]
11 12 22 25 64

// Find the minimum element in arr[3...4]
// and place it at beginning of arr[3...4]
11 12 22 25 64

Below is the program for the same:

C++

 // C++ program for implementation of // selection sort #include using namespace std;   // Function to swap two number void swap(int* xp, int* yp) {     int temp = *xp;     *xp = *yp;     *yp = temp; }   // Function to implement the selection // sort void selectionSort(int arr[], int n) {     int i, j, min_idx;       // One by one move boundary of     // unsorted subarray     for (i = 0; i < n - 1; i++) {           // Find the minimum element         // in unsorted array         min_idx = i;         for (j = i + 1; j < n; j++)             if (arr[j] < arr[min_idx])                 min_idx = j;           // Swap the found minimum element         // with the first element         swap(&arr[min_idx], &arr[i]);     } }   // Function to print an array void printArray(int arr[], int size) {     int i;       for (i = 0; i < size; i++) {         cout << arr[i] << " ";     }     cout << endl; }   // Driver Code int main() {     int arr[] = { 64, 25, 12, 22, 11 };     int n = sizeof(arr) / sizeof(arr);       // Function Call     selectionSort(arr, n);     cout << "Sorted array: \n";       // Print the array     printArray(arr, n);     return 0; }

Java

 // Java program for implementation of // selection sort import java.util.*; class GFG {   // Function to implement the selection // sort static void selectionSort(int arr[], int n) {     int i, j, min_idx;       // One by one move boundary of     // unsorted subarray     for (i = 0; i < n - 1; i++)     {           // Find the minimum element         // in unsorted array         min_idx = i;         for (j = i + 1; j < n; j++)             if (arr[j] < arr[min_idx])                 min_idx = j;           // Swap the found minimum element         // with the first element         int temp = arr[min_idx];         arr[min_idx]= arr[i];         arr[i] = temp;     } }   // Function to print an array static void printArray(int arr[], int size) {     int i;       for (i = 0; i < size; i++) {         System.out.print(arr[i]+ " ");     }     System.out.println(); }   // Driver Code public static void main(String[] args) {     int arr[] = { 64, 25, 12, 22, 11 };     int n = arr.length;       // Function Call     selectionSort(arr, n);     System.out.print("Sorted array: \n");       // Print the array     printArray(arr, n); } }   // This code is contributed by aashish1995

Python3

 # Python3 program for implementation of # selection sort   # Function to implement the selection # sort def selectionSort(arr, n):       # One by one move boundary of     # unsorted subarray     for i in range(n - 1):           # Find the minimum element         # in unsorted array         min_idx = i         for j in range(i + 1, n):             if (arr[j] < arr[min_idx]):                 min_idx = j           # Swap the found minimum element         # with the first element         arr[min_idx], arr[i] = arr[i], arr[min_idx]   # Function to print an array def printArray(arr, size):       for i in range(size):         print(arr[i], end = " ")       print()   # Driver Code if __name__ == "__main__":       arr = [64, 25, 12, 22, 11]     n = len(arr)       # Function Call     selectionSort(arr, n)     print("Sorted array: ")       # Print the array     printArray(arr, n)   # This code is contributed by ukasp

C#

 // C# program for implementation of // selection sort using System; public class GFG {   // Function to implement the selection // sort static void selectionSort(int []arr, int n) {     int i, j, min_idx;       // One by one move boundary of     // unsorted subarray     for (i = 0; i < n - 1; i++)     {           // Find the minimum element         // in unsorted array         min_idx = i;         for (j = i + 1; j < n; j++)             if (arr[j] < arr[min_idx])                 min_idx = j;           // Swap the found minimum element         // with the first element         int temp = arr[min_idx];         arr[min_idx]= arr[i];         arr[i] = temp;     } }   // Function to print an array static void printArray(int []arr, int size) {     int i;       for (i = 0; i < size; i++) {         Console.Write(arr[i]+ " ");     }     Console.WriteLine(); }   // Driver Code public static void Main(String[] args) {     int []arr = { 64, 25, 12, 22, 11 };     int n = arr.Length;       // Function Call     selectionSort(arr, n);     Console.Write("Sorted array: \n");       // Print the array     printArray(arr, n); } }   // This code is contributed by gauravrajput1

Javascript



Output:

Sorted array:
11 12 22 25 64

Tabular Difference between Insertion Sort and Selection Sort:

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