Largest subset whose all elements are Fibonacci numbers in C++

#include <iostream>
#include <vector>
#include <unordered_set>

// Function to generate Fibonacci numbers up to a given limit
std::vector<int> generateFibonacci(int limit) {
    std::vector<int> fibonacci;
    int a = 0, b = 1, c = 0;
    while (c <= limit) {
        fibonacci.push_back(c);
        a = b;
        b = c;
        c = a + b;
    }
    return fibonacci;
}

// Function to find the largest subset of Fibonacci numbers in an array
std::vector<int> largestFibonacciSubset(const std::vector<int>& arr) {
    // Generate Fibonacci numbers up to the maximum element in the array
    int max_element = *std::max_element(arr.begin(), arr.end());
    std::vector<int> fibonacci = generateFibonacci(max_element);

    // Create a set for faster lookup
    std::unordered_set<int> fibonacci_set(fibonacci.begin(), fibonacci.end());

    std::vector<int> result;
    for (int num : arr) {
        if (fibonacci_set.count(num)) {
            result.push_back(num);
        }
    }

    return result;
}

int main() {
    std::vector<int> arr = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11};

    std::vector<int> fibonacciSubset = largestFibonacciSubset(arr);

    std::cout << "Largest Fibonacci Subset: ";
    for (int num : fibonacciSubset) {
        std::cout << num << " ";
    }
    std::cout << std::endl;

    return 0;
}