what is the lambda function in CPP

In C++, a lambda function is an anonymous function that can be defined inline with the rest of your code. It allows you to create a function object on the fly, without having to define a separate function. Lambda functions can capture variables from the surrounding context and can be passed around like any other object. Here's an example of a lambda function in C++:

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

int main() {
    std::vector<int> nums{3, 6, 2, 7, 1, 9};

    // Sort the vector in descending order using a lambda function
    std::sort(nums.begin(), nums.end(), [](int a, int b) {
        return a > b;
    });

    // Print the sorted vector
    for (int num : nums) {
        std::cout << num << " ";
    }

    return 0;
}

In this example, the lambda function is used as the third argument to the `std::sort` algorithm. The function takes two integers as arguments and returns `true` if the first argument is greater than the second argument, indicating that the vector should be sorted in descending order.