def fill_graph_randomly(self, c=-1):
        if c == -1:
            c = floor(random() * 10000) + 10
        for i in range(c):
            # every vertex has max 100 edges
            for _ in range(floor(random() * 102) + 1):
                n = floor(random() * c) + 1
                if n != i:
                    self.add_pair(i, n, 1)