sorting using comparator in c++

To sort elements using a comparator in C++, you can follow these steps:

Define a custom comparator function that takes two elements as input and returns a boolean value indicating their order. The comparator function should have the following signature:

bool comparator(const T& a, const T& b);

Here, T represents the type of the elements being sorted.

Use the std::sort algorithm from the <algorithm> library to sort the elements. The std::sort function takes three parameters: the starting iterator, the ending iterator, and the comparator function. For example:

std::sort(startIterator, endIterator, comparator);

In this case, startIterator represents the iterator pointing to the first element to be sorted, endIterator represents the iterator pointing to one position past the last element to be sorted, and comparator is the custom comparator function.

The std::sort algorithm internally uses the comparator function to compare pairs of elements and determine their order. The comparator function should return true if the first element should come before the second element in the sorted sequence, and false otherwise.
After the sorting process, the elements will be rearranged in the specified order according to the comparator function.

Here's an example that demonstrates sorting integers in descending order using a custom comparator:

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

bool descendingComparator(const int& a, const int& b) {
    return a > b;
}

int main() {
    std::vector<int> numbers = {5, 2, 8, 1, 6};

    std::sort(numbers.begin(), numbers.end(), descendingComparator);

    for (const auto& number : numbers) {
        std::cout << number << " ";
    }

    return 0;
}

In this example, the descendingComparator function compares two integers a and b and returns true if a is greater than b. The std::sort algorithm uses this comparator to sort the numbers vector in descending order. Finally, the sorted elements are printed to the console: 8 6 5 2 1.