What is the usage of std::max in C++?

1 year ago
Emily Johnson
2 minutes

std::max is a function template in the C++ standard library that is used to compare two values and return the greater value.

The std::max function template has multiple overloaded versions that can be used to compare values of different types. Some commonly used versions include:

  1. std::max(a, b) function compares the values of a and b, and returns the greater value. Both a and b can be of the same type or types that can be implicitly converted to the same type.
  2. std::max(a, b, comp): Compares the sizes of a and b using a custom comparison function comp. Comp is a callable object (such as a function pointer, function object, or lambda expression) that takes two parameters and returns a value that can be converted to a bool type, indicating the relationship between a and b. If comp(a, b) returns true, then a is considered greater than b; otherwise, b is considered greater than or equal to a.
  3. Find and return the largest value in the initialization list “ilist”. This version can be used to compare multiple values.

Example of using std::max:

#include <iostream>
#include <algorithm>

int main() {
    int a = 5;
    int b = 10;
    int max_value = std::max(a, b);
    std::cout << "Max value: " << max_value << std::endl;

    double x = 3.14;
    double y = 2.718;
    double max_value2 = std::max(x, y);
    std::cout << "Max value: " << max_value2 << std::endl;

    auto comp = [](int a, int b) { return a % 10 < b % 10; };
    int max_value3 = std::max(a, b, comp);
    std::cout << "Max value: " << max_value3 << std::endl;

    int max_value4 = std::max({1, 2, 3, 4, 5});
    std::cout << "Max value: " << max_value4 << std::endl;

    return 0;
}

Output result:

Max value: 10
Max value: 3.14
Max value: 5
Max value: 5
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