Using minmax_element() with a lambda

You can use std::ranges::minmax_element() with a lambda function to customize the comparison logic. This is useful when you need to determine the minimum and maximum elements based on a specific criterion.

Example Scenario

Consider a Player class where each player has a Health attribute. We want to find the players with the minimum and maximum health using a lambda function.

Step 1: Define the Custom Type

1#include <algorithm>
2#include <iostream>
3#include <vector>
4
5class Player {
6 public:
7  Player(std::string Name, int Health)
8      : Name(Name), Health(Health) {}
9
10  std::string GetName() const { return Name; }
11  int GetHealth() const { return Health; }
12
13 private:
14  std::string Name;
15  int Health;
16};

Step 2: Use std::ranges::minmax_element() with Lambda

1#include <algorithm>
2#include <iostream>
3#include <vector>
4
Player Class|Show
5class Player {/*...*/};
18
19
20int main() {
21  std::vector<Player> Party {
22    Player("Roderick", 100),
23    Player("Anna", 200),
24    Player("Robert", 500)
25  };
26
27  auto [minIt, maxIt] = std::ranges::minmax_element(
28    Party,
29    [](const Player& a, const Player& b) {
30      return a.GetHealth() < b.GetHealth();
31    }
32  );
33
34  std::cout << "Player with the least health: "
35    << minIt->GetName() << " ("
36    << minIt->GetHealth() << ")\n";
37
38  std::cout << "Player with the most health: "
39    << maxIt->GetName() << " ("
40    << maxIt->GetHealth() << ")\n";
41}

1Player with the least health: Roderick (100)
2Player with the most health: Robert (500)

Explanation

• Custom Comparison: The lambda function is passed to std::ranges::minmax_element(), allowing the algorithm to compare Player objects based on their Health.
• Structured Binding: The result of std::ranges::minmax_element() is a pair of iterators, minIt and maxIt, which point to the elements with the minimum and maximum health, respectively.
• Output: The program prints the names and health of the players with the minimum and maximum health.

Using a lambda function with std::ranges::minmax_element() provides a flexible way to customize the comparison logic, enabling you to handle complex scenarios with ease.