## iterators
### Instructions
The Collatz Conjecture or 3x+1 problem can be summarized as follows:
Take any positive integer `n` .
- If `n` is even, you will divide `n` by 2 to get `n / 2` .
- If `n` is odd, you will multiply `n` by 3 and add 1 to get `3n + 1` .
Repeat the process indefinitely. The conjecture states that no matter which number you start with, you will always reach 1 eventually.
But sometimes the number grow significantly before it reaches 1. This can lead to an integer overflow and makes the algorithm unsolvable within the range of a number in u64. You will not have to worry about that in this exercise.
Given a number `n` , return the number of steps required to reach 1.
Examples:
Starting with n = 16, the steps would be as follows:
0- 16
1- 8
2- 4
3- 2
4- 1
Resulting in 4 steps. So for input n = 16, the return value would be 4.
### Notions
- [Trait Iterator ](https://doc.rust-lang.org/std/iter/trait.Iterator.html )
- [Collatz Conjecture ](https://en.wikipedia.org/wiki/Collatz_conjecture )
### Expected functions
```rust
struct Collatz {
v: u64,
}
impl Iterator for Collatz {}
pub fn collatz(n: u64) -> Option< u64 > {}
```
### Usage
Here is a program to test your function.
```rust
use iterators::*;
fn main() {
println!("{:?}", collatz(4));
println!("{:?}", collatz(5));
println!("{:?}", collatz(6));
println!("{:?}", collatz(7));
println!("{:?}", collatz(12));
}
```
And its output:
```console
$ cargo run
Some(2)
Some(5)
Some(8)
Some(16)
Some(9)
$
```
