What Is Big O Notation in Data Structure Explain With the Help of a Graph?

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Angela Bailey

What Is Big O Notation in Data Structure Explain With the Help of a Graph?

When analyzing algorithms and data structures, it is essential to understand their efficiency. Big O notation is a mathematical notation used to describe the performance of an algorithm in terms of its input size. It allows us to analyze how an algorithm’s execution time or space requirements grow as the input size increases.

Understanding Big O Notation

Big O notation provides a standardized way to express the upper bound or worst-case scenario for the time complexity of an algorithm. It describes how the algorithm’s performance scales with respect to the size of the input.

The notation is written as “O(f(n)),” where f(n) represents a function that denotes the number of operations performed by an algorithm as a function of the input size (n). The ‘O’ in Big O stands for “order of” or “on the order of.”

An Example: Linear Search

Let’s consider a simple example to illustrate Big O notation using linear search, which involves searching for a specific element in an array:

• Step 1: Start from the first element and compare it with the Target element.
• Step 2: If they match, return the index.
• Step 3: If not, move on to the next element and repeat Steps 1 and 2 until either a match is found or all elements have been checked.

In this case, we can express the time complexity using Big O notation as O(n), where ‘n’ represents the number of elements in the array. This indicates that in the worst-case scenario, we may need to iterate through all elements in the array to find the Target element.

Graphical Representation

Visualizing the relationship between input size and algorithmic performance can provide a clearer understanding of Big O notation. Let’s represent the time complexity of various algorithms using a graph:

The x-axis represents the input size, and the y-axis represents the number of operations performed by the algorithm. The graph demonstrates how different functions (f(n)) grow as ‘n’ increases.

Common Big O Notations

Here are some commonly encountered Big O notations and their corresponding growth rates:

• O(1) – Constant Time: The algorithm’s execution time remains constant regardless of the input size. Example: accessing an element in an array using its index.
• O(log n) – Logarithmic Time: The algorithm’s execution time grows logarithmically with respect to the input size. Example: binary search.
• O(n) – Linear Time: The algorithm’s execution time increases linearly with respect to the input size.

Example: linear search, iterative traversal of an array.

• O(n log n) – Log-Linear Time: The algorithm’s execution time grows in proportion to ‘n’ multiplied by logarithm of ‘n’. Example: merge sort, quicksort.
• O(n^2) – Quadratic Time: The algorithm’s execution time grows quadratically with respect to the input size. Example: nested loops for matrix multiplication.