Counting Algorithms

# How to Count Elements in a Custom Container Using std::ranges::count()

## How can I count elements in a custom container using std::ranges::count()?

To count elements in a custom container using std::ranges::count(), you need to ensure your container meets the requirements for a range. This means your container should provide begin() and end() functions that returnÂ iterators.

Here's an example of how to count elements in a customÂ container:

#include <algorithm>
#include <iostream>
#include <vector>

class CustomContainer {/*...*/};

int main() {
CustomContainer<int> Numbers;

auto Fours{std::ranges::count(Numbers, 4)};
std::cout << "Count of fours: " << Fours;
}
Count of fours: 2

In thisÂ example:

• CustomContainer is a template class that stores elements in a std::vector.
• The add() method adds elements to the container.
• The begin() and end() methods return iterators to the beginning and end of the container, respectively.

By ensuring CustomContainer provides begin() and end() methods, it meets the requirements of a range, allowing us to use std::ranges::count() to countÂ elements.

This approach works for any type of custom container, as long as it provides the necessary iterator access functions. This makes std::ranges::count() a flexible tool for counting elements in various types of containers in C++20 andÂ later.

This Question is from the Lesson:

### Counting Algorithms

An introduction to the 5 main counting algorithms in the C++ standard library: count(), count_if(), any_of(), none_of(), and all_of()

Answers to questions are automatically generated and may not have been reviewed.

This Question is from the Lesson:

### Counting Algorithms

An introduction to the 5 main counting algorithms in the C++ standard library: count(), count_if(), any_of(), none_of(), and all_of()

Part of the course:

## Professional C++

Comprehensive course covering advanced concepts, and how to use them on large-scale projects.

Free, unlimited access

### This course includes:

• 124 Lessons
• 550+ Code Samples
• 96% Positive Reviews
• Regularly Updated
• Help and FAQ
Free, Unlimited Access

### Professional C++

Comprehensive course covering advanced concepts, and how to use them on large-scale projects.