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  4. Trees: Is This a Binary Search Tree?
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Trees: Is This a Binary Search Tree?

  • Dan_Golding + 0 comments

    I ended up with pretty much the same code but instead of a closure variable I just passed the variable in. I used a single element list since it's gets passed by reference which allows changes to persist when going back down the call stack:

    def checkBST(root):
    return(check_in_order(root,[-1]))
    
def check_in_order(root,prev):
    result = True
    if root.left is not None:
        result &= check_in_order(root.left,prev)
    if prev[0] >= root.data:
        return False
    prev[0] = root.data
    if root.right is not None:
        result &= check_in_order(root.right,prev)
    return result