Sorting algorithms are the backbone of data organization, and Insertion Sort is a methodical and adaptable technique. Its simplicity and versatility make it a valuable tool in a programmer's arsenal. In this SEO blog, we'll unravel the intricacies of Insertion Sort, provide code examples in Python, explore its time complexity, and conquer a LeetCode challenge using this sorting algorithm.

Demystifying Insertion Sort

Insertion Sort is an in-place, comparison-based sorting algorithm that constructs the final sorted array one element at a time. It systematically places each element in its proper position within the existing sorted portion of the array.

Insertion Sort at a Glance:

1. Begin with the second element, treating it as the 'key.'

2. Compare the 'key' with elements in the sorted part, shifting larger elements to the right.

3. Insert the 'key' into its correct position within the sorted portion.

4. Repeat until all elements are sorted.

Python Implementation of Insertion Sort

Let's dive into the Python implementation of Insertion Sort:

def insertion_sort(arr):
    n = len(arr)
    for i in range(1, n):
        key = arr[i]
        j = i - 1
        while j >= 0 and arr[j] > key:
            arr[j + 1] = arr[j]
            j -= 1
        arr[j + 1] = key
    return arr

Analyzing Time Complexity

Insertion Sort's time complexity is O(n^2) in the worst case, making it more suitable for smaller datasets. The nested loop structure, coupled with element shifting, contributes to this complexity.

Solving a LeetCode Problem using Insertion Sort

Problem: LeetCode 147 - Insertion Sort List

Given the head of a singly linked list, sort the list using the Insertion Sort algorithm.

Solution using Insertion Sort: Traverse the linked list and insert each node into the sorted portion of the list.

class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

def insertion_sort_list(head):
    dummy = ListNode()
    current = head
    while current:
        prev = dummy
        while prev.next and prev.next.val < current.val:
            prev = prev.next
        temp = current.next
        current.next = prev.next
        prev.next = current
        current = temp
    return dummy.next

Conclusion

Insertion Sort, with its adaptability and practicality, offers valuable insights into sorting. By grasping its logic, implementing it in Python, and solving real-world challenges like the LeetCode problem, you gain a versatile sorting tool. Whether you're a coding novice exploring sorting or an experienced programmer revisiting the basics, Insertion Sort strikes a balance between simplicity and effectiveness.

Happy coding and sorting! 🚀🔍🧠