Encode number

#[test]
fn t1() {
    let start = std::time::Instant::now();
    let val = Solution::encode(23);
    let expected = "1000".to_string();
    log_result!(val == expected, "t1", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t2() {
    let start = std::time::Instant::now();
    let val = Solution::encode(107);
    let expected = "101100".to_string();
    log_result!(val == expected, "t2", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t3() {
    let start = std::time::Instant::now();
    let val = Solution::encode(0);
    let expected = "".to_string();
    log_result!(val == expected, "t3", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t4() {
    let start = std::time::Instant::now();
    let val = Solution::encode(1);
    let expected = "0".to_string();
    log_result!(val == expected, "t4", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t5() {
    let start = std::time::Instant::now();
    let val = Solution::encode(2);
    let expected = "1".to_string();
    log_result!(val == expected, "t5", start, &expected, &val);
    assert_eq!(val, expected);
}