copying_from_others.txt

// Notable improvement: Use int instead of {'x':x, 'y':y} for positions
// Notable improvement: If there are no negation symbols, edges between stones of the same color are forced.
//   This can be pre-computed, as well -- so each validate() call can share the info.

findSolution(path, visited, required, edgeRequired, exitsRemaining, areas, segment)


step 1:
determineAuxilaryRequired(); // Determine lines which are required (owing to adjest stones of the same color)
required = getNodesByType(NODE_TYPE.REQUIRED)
edgeRequired = getEdgesByType(EDGE_TYPE.REQUIRED)
exitsRemaining = getNodesByType(NODE_TYPE.EXIT).length;

for each start point:
  findSolution(path = [{x, y}], visited = [{x, y}], ...)
  if (solution) return solution
  return null

current_node = path.tail()
prev_node = path.tail() - 1

[areas, segment] = separateAreasStep() // *interesting*
if (!areas) // somehow determined that an area we're including is wrong.

if current_node.end == true:
  if (!checkLastArea(previous_node, current_node, areas, segment)) // *interesting*
    exitsRemaining--
  else if (!checkRequiredNodes(path, required))
    exitsRemaining--
  else if (!checkRequiredEdges(path, edgeRequired))
    exitsRemaining--
  else
    return path // success

  if (exitsRemaining == 0) return false;

  for next_node in [left, up, down, right]:
    recurse


checkLastArea(previous_node, current_node, areas, segment) {
  if previous_node is on an edge: