at first I added test from description:
@Test
public void testFirst() {
int[][] firstPyramid = new int[][]{
{3},
{7,4},
{2,4,6},
{8,5,9,3}
};
assertEquals(23, LongestSlideDown.longestSlideDown(firstPyramid));
}

this is very helpful thank you

For learning purpose will be good to add constructors to commented class TreeNode like this:
public static class TreeNode {
public int value;
public TreeNode left;
public TreeNode right;

    public TreeNode(int value) {
        this.value = value;
        this.left = this.right = null;
    }
    public TreeNode(int value, TreeNode left, TreeNode right) {
        this.value = value;
        this.left = left;
        this.right = right;
    }

}

fixed, thanx

Sorry, may be typo in description - not "euclidiean", but "euclidean". With all my respect.

"Efficiency is not a key point of this part of the series" - but I have time out - 16s and so many random tests(
I am not complain!)

Strange, 6 points for so easy task, as I see

for Java, I change parameter in function from int to long. There is a test where num = -2147483648

Nice Kata. I solved this kata only when read about
"Little-endian" and "Big-endian".

Yes, this is the point! Thats why in IT companies Business analysts are working hard.

this also get pass.

Approved