def adjacency(tree):
    """
    Construct the adjacency matrix of the tree
    :param tree:
    :return:
    """
    dd = ids(tree)
    N = len(dd)
    A = np.zeros((N, N))

    def _adj(node):
        if np.isscalar(node):
            return
        elif isinstance(node, tuple) and len(node) == 2:
            A[dd[node], dd[node[0]]] = 1
            A[dd[node[0]], dd[node]] = 1
            _adj(node[0])

            A[dd[node], dd[node[1]]] = 1
            A[dd[node[1]], dd[node]] = 1
            _adj(node[1])

    _adj(tree)
    return A