Скачать или смотреть How to Find the Last Occurrence of Each Number in a Sorted Array

A step-by-step guide to modifying an algorithm to retrieve the last occurrence of numbers from a sorted array, with Python code examples.
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Finding the Last Occurrence of Numbers in a Sorted Array

When working with sorted arrays, a common problem developers face is efficiently finding occurrences of numbers. This guide addresses how to create a function that returns the last occurrence of each number from 0 to 9 in a sorted array. If you've ever found yourself needing to enhance a binary search algorithm to solve this problem, you’re in the right place!

Understanding the Problem

You might already have a function that retrieves the first occurrence of each number in a sorted array, but what if you need the last? In this case, consider the following sorted array:

[[See Video to Reveal this Text or Code Snippet]]

If you run a function similar to the one below to find the last occurrence, you would like to get the result:

[[See Video to Reveal this Text or Code Snippet]]

The Solution Approach

Binary Search Overview

Binary search is a great algorithm to leverage in these situations due to its efficiency. The main logic involves dividing the search space in half, which leads to a logarithmic time complexity. However, for getting the last occurrence, some tweaks are necessary.

The Modified Function

Here’s the revised version of a function that seeks the last occurrence of each number in a sorted array:

[[See Video to Reveal this Text or Code Snippet]]

Explanation

Ending Condition:

Instead of returning left, we return left - 1. This adjustment helps us find the last index where the value occurs correctly.

Recursive Calls:

If the middle value (a[mid]) is less than or equal to the searched value (val), the search continues on the right half of the array.

Returning the Result:

After looping through the numbers, you can apply the upper function in a loop from 0 to 9, thus printing the last occurrence of each number efficiently.

Sample Usage

You can implement a simple loop to invoke the upper function:

[[See Video to Reveal this Text or Code Snippet]]

This will print the correct last occurrences for each number from 0 to 9.

Conclusion

In summary, modifying your binary search to identify the last occurrence of numbers in a sorted array can significantly enhance the usability of data querying. By simply adjusting the return value and maintaining the same recursive logic, you streamline the process. Now, you can easily find both the first and last occurrences without any hassle.

Happy coding, and feel free to reach out if you have further questions or need more clarifications!