Edges Until Connected

Problem

Add undirected edges one at a time and report when the graph first becomes connected.

Return the number of edges processed at the moment all n nodes share a single component; count includes the edge that completed the connection. If the given edge list never connects the graph, return -1. A graph with n <= 1 is already connected and needs 0 edges.

Hint

Track the component count as unions succeed and stop the first time it equals 1.

Test cases

case 1

in: [4,[[0,1],[1,2],[2,3]]]

expected: 3

case 2

in: [4,[[0,1],[1,2],[2,3],[0,3]]]

expected: 3

case 3

in: [4,[[0,1],[2,3]]]

expected: -1

case 4

in: [1,[]]

expected: 0

case 5

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

expected: 2

Starter codePython

def edges_until_connected(n, edges):
    # Your code here
    pass

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