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📌 Inversion Count in an Array (HARD) | Road to Internship

In this video, we solve an important DSA problem frequently asked in interviews and coding tests.

🔹 Problem Statement

Given an array of integers, find the Inversion Count of the array.

🔹 What is Inversion Count?

Inversion Count shows how far (or how close) an array is from being sorted.

If the array is already sorted, the inversion count is 0

If the array is sorted in reverse order, the inversion count is maximum

Formal Definition:
Two elements a[i] and a[j] form an inversion if
a[i] is greater than a[j] and the index i comes before index j.

🧪 Examples

Example 1

Input:
N = 5
Array = 2, 4, 1, 3, 5

Output:
3

Explanation:
Inversions are (2,1), (4,1), (4,3)


Example 2

Input:
N = 5
Array = 2, 3, 4, 5, 6

Output:
0

Explanation:
The array is already sorted.


Example 3

Input:
N = 3
Array = 5, 5, 5

Output:
0

Explanation:
All elements are equal and already in sorted order.

💡 Hint

A sorting-based approach is used to solve this problem efficiently.