Maximum alternating subarray sum

#[test]
fn t1() {
    let start = std::time::Instant::now();
    let val = Solution::maximum_alternating_subarray_sum(vec![3, -1, 1, 2]);
    let expected = 5;
    log_result!(val == expected, "t1", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t2() {
    let start = std::time::Instant::now();
    let val = Solution::maximum_alternating_subarray_sum(vec![2, 2, 2, 2, 2]);
    let expected = 2;
    log_result!(val == expected, "t2", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t3() {
    let start = std::time::Instant::now();
    let val = Solution::maximum_alternating_subarray_sum(vec![1]);
    let expected = 1;
    log_result!(val == expected, "t3", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t4() {
    let start = std::time::Instant::now();
    let val = Solution::maximum_alternating_subarray_sum(vec![-1, -2, -3]);
    let expected = 1;
    log_result!(val == expected, "t4", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t5() {
    let start = std::time::Instant::now();
    let val = Solution::maximum_alternating_subarray_sum(vec![5, -3, 10, -1, 2]);
    let expected = 21;
    log_result!(val == expected, "t5", start, &expected, &val);
    assert_eq!(val, expected);
}