<doocs>0098.Validate Binary Search Tree_1.py
def dfs(root):
    nonlocal prev
    if root is None:
        return True
    if not dfs(root.left):
        return False
    if prev >= root.val:
        return False
    prev = root.val
    if not dfs(root.right):
        return False
    return True
def sample_funcname ( var_1 ) :
    nonlocal var_2
    if var_1 is None :
        return True
    if not var_0 ( var_1.left ) :
        return False
    if var_2 >= var_1.val :
        return False
    var_2 = var_1.val
    if not var_0 ( var_1.right ) :
        return False
    return True
