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[1] 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 <bits/stdc++.h> 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[0]); // 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 |
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 <bits/stdc++.h> 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[0]); // Function Call selectionSort(arr, n); cout << "Sorted array: \n" ; // Print the array printArray(arr, n); return 0; } |
Sorted array: 11 12 22 25 64
Tabular Difference between Insertion Sort and Selection Sort:
|
Insertion Sort | Selection Sort |
---|---|---|
1. | Inserts the value in the presorted array to sort the set of values in the array. | Finds the minimum / maximum number from the list and sort it in ascending / descending order. |
2. | It is a stable sorting algorithm. | It is an unstable sorting algorithm. |
3. | The best-case time complexity is O(N) when the array is already in ascending order. | There is no best case the time complexity is O(N2) in all cases. |
4. | The number of comparison operations performed in this sorting algorithm is less than the swapping performed. | The number of comparison operations performed in this sorting algorithm is more than the swapping performed. |
5. | It is more efficient than the Selection sort. | It is less efficient than the Insertion sort. |
6. | Here the element is known beforehand, and we search for the correct position to place them. | The location where to put the element is previously known we search for the element to insert at that position. |
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