# Writing a Binary Search in Pseudocode

Binary search is a commonly used algorithm in computer science that involves searching for a specific value in a sorted list or array. It is an efficient way to search for a value as it can quickly narrow down the search space by dividing it in half with each comparison. However, implementing binary search can be challenging, especially for beginners.

One way to make the implementation of binary search easier is to use pseudocode. Pseudocode is a high-level description of a program that uses a mixture of natural language and programming language syntax to describe the steps involved in a particular algorithm.

By using pseudocode, we can focus on the logic of the algorithm without worrying about the specifics of the programming language. In the case of binary search, pseudocode can help us to understand the steps involved in the algorithm and how to implement them in code.

We follow the pseudocode standard set by the main computer science exam board in the UK, AQA, allowing a universal set of functions and operators to be used. This makes it much easier for programmers to understand each other's pseudocode!

## Understanding Binary Search

- Binary search is a search algorithm that is used to find a specific value in a sorted list or array.
- It is a very efficient algorithm that can quickly find the target value with a small number of comparisons.

To perform a binary search, we first need to have a sorted list or array. We start by comparing the target value with the middle element of the list. If the target value is equal to the middle element, we return the index of the middle element. If the target value is greater than the middle element, we search the right half of the list. Otherwise, we search the left half of the list. We repeat this process until we find the target value or determine that it is not in the list.

## A Pseudocode Binary Search

The pseudocode for binary search can be written as follows:

First of all, **we need to create a data set to sort**. This can be done by just declaring an array and a subroutine in our pseudocode.

### Explaing the Pseudocode

In this pseudocode, we initialize the left and right indices to the first and last elements of the list, respectively. We then enter a loop that continues until the left index is greater than the right index. Inside the loop, we calculate the middle index and compare the middle element to the target value.

If the middle element is equal to the target value, we return the middle index. Otherwise, we update the left or right index based on whether the target value is greater or less than the middle element. If we exit the loop without finding the target value, we return -1.

Overall, binary search is a powerful algorithm that can quickly find a specific value in a sorted list or array. With the pseudocode provided, you should be able to implement binary search in your own programs.

### Variables Used

We need to use an array or list of sorted elements, a target value we want to find in the array, and two pointers to keep track of the left and right boundaries of our search range.

### Main Algorithm

Now that we have our variables defined, let' take a look at the pseudocode for the binary search algorithm.

- Set the left pointer to the first element of the array and the right pointer to the last element.
- While the left pointer is less than or equal to the right pointer:
- Calculate the middle index as the average of the left and right pointers.
- If the middle element is equal to the target value, return its index.
- If the middle element is less than the target value, set the left pointer to the middle index + 1.
- If the middle element is greater than the target value, set the right pointer to the middle index - 1.
- If the target value is not found in the array, return -1.

In summary, the binary search algorithm works by repeatedly dividing the search range in half until the target value is found or the search range is empty. This makes it a very efficient algorithm for finding elements in a sorted array.