Find the maximum length of valid subsequence ii

#[test]
fn test_example1() {
    let start = std::time::Instant::now();
    let val = Solution::maximum_length(vec![1, 2, 3, 4, 5], 2);
    let expected = 5;
    log_result!(val == expected, "test_example1", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_example2() {
    let start = std::time::Instant::now();
    let val = Solution::maximum_length(vec![1, 4, 2, 3, 1, 4], 3);
    let expected = 4;
    log_result!(val == expected, "test_example2", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_k1() {
    let start = std::time::Instant::now();
    let val = Solution::maximum_length(vec![3, 1, 4, 1, 5], 1);
    let expected = 5;
    log_result!(val == expected, "test_k1", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_same_elements() {
    let start = std::time::Instant::now();
    let val = Solution::maximum_length(vec![3, 3, 3], 3);
    let expected = 3;
    log_result!(val == expected, "test_same_elements", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_single_valid_pair() {
    let start = std::time::Instant::now();
    let val = Solution::maximum_length(vec![1, 2, 4], 5);
    let expected = 2;
    log_result!(val == expected, "test_single_valid_pair", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_small() {
    let start = std::time::Instant::now();
    let val = Solution::maximum_length(vec![1, 2], 3);
    let expected = 2;
    log_result!(val == expected, "test_small", start, &expected, &val);
    assert_eq!(val, expected);
}