Insertion Sort – Python
Insertion sort is a simple sorting algorithm that works by iteratively inserting each element of an unsorted list into its correct position in a sorted portion of the list.
Insertion Sort
- The insertionSort function takes an array arr as input. It first calculates the length of the array (n). If the length is 0 or 1, the function returns immediately as an array with 0 or 1 element is considered already sorted.
- For arrays with more than one element, We start with second element of the array as first element in the array is assumed to be sorted.
- Compare second element with the first element and check if the second element is smaller then swap them.
- Move to the third element and compare it with the first two elements and put at its correct position
- Repeat until the entire array is sorted.
The provided example demonstrates the sorting process using the insertion sort algorithm. The initial array [12, 11, 13, 5, 6] is subjected to the insertionSort function. After sorting, the array should be [5, 6, 11, 12, 13]. The code prints the sorted array as the final output.
def insertionSort(arr):
n = len(arr) # Get the length of the array
if n <= 1:
return # If the array has 0 or 1 element, it is already sorted, so return
for i in range(1, n): # Iterate over the array starting from the second element
key = arr[i] # Store the current element as the key to be inserted in the right position
j = i-1
while j >= 0 and key < arr[j]: # Move elements greater than key one position ahead
arr[j+1] = arr[j] # Shift elements to the right
j -= 1
arr[j+1] = key # Insert the key in the correct position
# Sorting the array [12, 11, 13, 5, 6] using insertionSort
arr = [12, 11, 13, 5, 6]
insertionSort(arr)
print(arr)
Output:
Sorted array is:
[5, 6, 11, 12, 13]
Time Complexity: O(N2)
Auxiliary Space: O(1)
Please refer complete article on Insertion Sort for more details!
Python Program for Insertion Sort – FAQs
What is Insertion Sort?
Insertion Sort is a simple sorting algorithm that builds the final sorted array (or list) one element at a time. It is much like sorting a hand of playing cards. The algorithm takes one element at a time and places it in its correct position relative to the already sorted part of the array.
Is Insertion Sort stable?
Yes, Insertion Sort is a stable sorting algorithm, meaning that it preserves the relative order of elements with equal values.
Can Insertion Sort be used for other data structures besides arrays?
While Insertion Sort is primarily used on arrays or lists, it can be adapted to other data structures like linked lists.
Is Insertion Sort better than Bubble Sort?
Insertion Sort generally performs better than Bubble Sort in practical scenarios. It requires fewer swaps (insertion) and can be faster for nearly sorted data. Both have a worst-case time complexity of O(n^2), but Insertion Sort performs fewer operations in practice.
