backtrace function
Backtrace according to the parent records and return the path. (including both start and end nodes) @param {Node} node End node @return {Array.<Array.
Implementation
List backtrace(node) {
var path = [[node.x, node.y]];
while (node.parent != null) {
node = node.parent;
path.add([node.x, node.y]);
}
return path.reversed.toList();
}