s``.

    Parameters
    ----------
    input_sets : list
        List of sets that represent the lhs side of the einsum subscript
    output_set : set
        Set that represents the rhs side of the overall einsum subscript
    idx_dict : dictionary
        Dictionary of index sizes
    memory_limit : int
        The maximum number of elements in a temporary array

    Returns
    -------
    path : list
        The greedy contraction order within the memory limit constraint.

    Examples
    --------
    >>> isets = [set('abd'), set('ac'), set('bdc')]
    >>> oset = set()
    >>> idx_sizes = {'a': 1, 'b':2, 'c':3, 'd':4}
    >>> _greedy_path(isets, oset, idx_sizes, 5000)
    [(0, 2), (0, 1)]
    r