getDepth' n t =
    let l = getDepth' (n - 1) $ left t
        r = getDepth' (n - 1) $ right t
    in [value t] : zipWith (++) l r
getDepth' n t =
    let l = getDepth' (n - 1) $ left t
        r = getDepth' (n - 1) $ right t
    in [value t] : zipWith (++) l r
getDepth' n t =
    let l = getDepth' (n - 1) $ left t
        r = getDepth' (n - 1) $ right t
    in [value t] : zipWith (++) l r