Sorting a Vector of Pairs in Descending Order in C

In C , you can sort a vector of pairs in descending order using the std::sort function from the algorithm header, along with a custom comparator. This article will demonstrate how to achieve this and provide an explanation of the process.

Prerequisites

To demonstrate this, we'll need to include the necessary headers and then create a vector of pairs. Here's a simple example:

Include Necessary Headers

The following headers are required:

for input/output. for using the vector container. for the std::sort function.

Create a Vector of Pairs

This example initializes a vector of pairs with some sample values:

std::vectorstd::pairint, int vec  {{1, 2}, {3, 1}, {2, 3}, {4, 0}};

Sorting the Vector

To sort the vector in descending order, use the std::sort function with a custom comparator. The comparator is a lambda function that compares the pairs based on the descending order of their values. Here's the code:

std::sort((), vec.end(), [](const std::pairint, int a, const std::pairint, int b) {
    return   ;  // Compare pairs for descending order based on the first element
});

Printing the Sorted Pairs

Finally, the sorted pairs are printed to the console:

for (const auto p : vec) {
    std::cout  "("    ", "    ") ";
}

Explanation

The std::sort function sorts elements in ascending order by default. Therefore, to sort in descending order, a custom comparator is necessary. In the provided lambda function, the comparison is based on the .first element of the pairs. This ensures that the pairs are sorted based on the first element in descending order.

Key Points

The std::sort function sorts elements in ascending order by default. To achieve descending order, a custom comparator must be provided. The lambda function can be adjusted to sort based on the first or second element of the pairs. For example, to sort by the first element only in descending order, the lambda function would compare and Other overloads of the sort function can be used with a function, functor, or lambda that returns true if the first element comes before the second.

Resources for Further Learning

For further reading and more detailed information, the following websites are handy:

- std::sort - std::sort

These resources include documentation and examples that can aid in understanding and implementing sorting in C .