이진 탐색 트리 (Binary search tree)

class DeletableSet:
    __slots__ = ['_parent']

    def __init__(self, size):
        self._parent = list(range(size))

    def get_greater_or_equal(self, x):
        if (par := self._parent[x]) == x:
            return x
        while (gpar := self._parent[par]) != par:
            self._parent[x] = gpar
            x, par = par, gpar
        return par

    def delete(self, x):
        if (root_x := self.get_greater_or_equal(x)) == (
            root_y := self.get_greater_or_equal(x + 1)
        ):
            raise ValueError
        self._parent[root_x] = root_y