crossingCount method
Implementation
int crossingCount(HashMap<Node, int> northernNodes, Node? n1, Node? n2) {
final indexOf = (Node node) => northernNodes[node]!;
var crossing = 0;
final parentNodesN1 = nodeData[n1]!.predecessorNodes;
final parentNodesN2 = nodeData[n2]!.predecessorNodes;
parentNodesN2.forEach((pn2) {
final indexOfPn2 = indexOf(pn2);
parentNodesN1.where((it) => indexOfPn2 < indexOf(it)).forEach((element) {
crossing++;
});
});
return crossing;
}