Maximum subarray

#[test]
fn test_all_positive() {
    let start = std::time::Instant::now();
    let val = Solution::max_sub_array(vec![5, 4, -1, 7, 8]);
    let expected = 23;
    log_result!(val == expected, "test_all_positive", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_example_1() {
    let start = std::time::Instant::now();
    let val = Solution::max_sub_array(vec![-2, 1, -3, 4, -1, 2, 1, -5, 4]);
    let expected = 6;
    log_result!(val == expected, "test_example_1", start, &expected, &val);
    assert_eq!(val, expected);
}

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

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

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