O(n)
Linear time - grows directly with input size.
Example: Single loop through array.
O(log n)
Logarithmic time - grows very slowly.
Example: Binary search in sorted array.
O(n log n)
Linearithmic time - efficient for many problems.
Example: Merge sort, using map in a loop.
O(n²)
Quadratic time - grows quickly with input size.
Example: Nested loops, brute force solutions.