O Notation and Time Complexity

What is “Big O notation” and “time complexity”?

Code examples demonstrating the following complexity classes:

O(1) - constant time (inserting elements at the beginning of a linked list)
O(n) - linear time (summing up all elements of an array)
O(n²) - quadratic time (sorting an array with Insertion Sort)
O(log n) - logarithmic time (finding an element within a sorted array using binary search)
O(n log n) - quasi-linear time (sorting an array with Quicksort)

The code belongs to this article:

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