Function bst_tree_height

tests/test_bst_tree.rs:78–85

()

#[test]
fn bst_tree_height() {
    // 升序数列，使BST退化成一个linked list
    let mut tree = Tree::default();
    for v in 0..100 {
        tree.insert(v, v);
    }
    assert_eq!(tree.height(), 100);
}

#[test]
fn is_bst() {