Learn Sorting Algorithms

Efficiently organizing data is essential in software development. In C++, the Standard Template Library (STL) provides robust, highly optimized algorithms for sorting sequences. The two primary sorting algorithms are std::sort and std::stable_sort.

Both algorithms accept a custom comparator, allowing you to define exactly how elements should be ordered. The comparator must define a strict weak ordering and should be consistent and free of side effects.

main.cpp


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

struct Person {
    std::string name;
    int age;
};

int main() 
{
    std::vector<Person> people = {
        {"Alice", 30},
        {"Bob", 25},
        {"Charlie", 35},
        {"Diana", 25}
    };

    // Sort by age, then by name
    std::sort(people.begin(), people.end(),
        [](const Person& a, const Person& b) {
            if (a.age != b.age) return a.age < b.age;
            return a.name < b.name;
        });

    for (const auto& person : people) 
        std::cout << person.name << " (" << person.age << ")\n";
}

Note

Use std::stable_sort when you need to preserve the relative order of equal elements.

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Section 3. Chapter 4

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