Moralization Edges Added

Problem

Moralizing a directed acyclic graph connects every pair of parents that share a child unless they are already adjacent, then drops edge directions. Given edges as [parent, child] pairs, return the number of distinct undirected edges that moralization adds. Return 0 for malformed inputs.

Hint

Count each unmarried parent pair once, even when the parents share several children.

Test cases

case 1

in: [[[0,2],[1,2]]]

expected: 1

case 2

in: [[[0,2],[1,2],[0,1]]]

expected: 0

case 3

in: [[[0,2],[1,2],[3,2]]]

expected: 3

case 4

in: [[[0,3],[1,3],[0,4],[1,4]]]

expected: 1

case 5

in: [[[0,2,1]]]

expected: 0

Starter codePython

def moralization_edges_added(edges):
    # Your code here
    pass

5 test cases · run your code against them in the editor