import torch


def sort(row, col):
    row, perm = row.sort()
    col = col[perm]
    return row, col


def permute(row, col, num_nodes, node_rid=None, edge_rid=None):
    num_edges = row.size(0)

    # Randomly reorder row and column indices.
    if edge_rid is None:
        edge_rid = torch.randperm(num_edges).type_as(row)
    row, col = row[edge_rid], col[edge_rid]

    # Randomly change row indices to new values.
    if node_rid is None:
        node_rid = torch.randperm(num_nodes).type_as(row)
    row = node_rid[row]

    # Sort row and column indices based on changed values.
    row, col = sort(row, col)

    # Revert previous row value changes to old indices.
    row = node_rid.sort()[1][row]

    return row, col