Answer

Rust

fn get_fibonacci(n: usize) -> Vec<i64> {
    let mut numbers = vec![0i64, 1];
    while numbers.len() < n {
        let next_number = numbers[numbers.len() - 1] + numbers[numbers.len() - 2];
        numbers.push(next_number);
    }
    numbers
}
fn zeckendorf_representation(mut n: i64) -> Vec<i64> {
    let numbers = get_fibonacci(50); // 50 is basically enough, otherwise it will be too slow/overflow
    let mut result = Vec::new();
    let mut i = numbers.len() - 1;
    while n > 0 && i > 0 {
        if numbers[i] <= n {
            n -= numbers[i];
            result.push(numbers[i]);
        }
        if i > 0 { i -= 1; }
    }

    result
}

fn main() {
println!("{:?}", zeckendorf_representation(64));
println!("{:?}", zeckendorf_representation(4));
}

Python

def fib(n):
    l = []
    a, b = 0, 1
    while b < n:
        a, b = b, a+b
        l.append(a)
    return l

def zec(n):
    l = []
    nums = fib(n)
    while len(nums) > 0:
        if max(nums) <= n - sum(l):
            l.append(max(nums))
            nums.pop()
        else:
            nums.pop()
    return l