two rivers are considered to be connected iff they share at least one vertex (no matter inner vertex or end vertex)

example 1:
2
2
-1 0
1 0
2
0 1
0 -1
not connected, because their intersection (0, 0) is not a vertex of river 1 or river 2

example 2:
2
2
-1 0
1 0
3
0 1
0 0
0 -1
not connected, because (0, 0) is not a vertex of River 1

example 3:
2
3
0 1
0 0
0 -1
3
-1 0
0 0
1 0
connected, because (0, 0) appears on both rivers