open-closed-search.txt

# input: startingNode

openList = []      # nodes we have discovered but haven't visited yet
closedList = []    # nodes we have already visited, store so we don't go back to them

# if the open list is a stack, we have DFS
# if the open list is a queue, we have BFS
# if the open list is a min/max-heap that uses some function of node properties, we have heuristic search
# the closed list can be a simple set; order is not important

# the starting node is all we've "discovered" so far
openList.add(startingNode)

# as long as there's something left to explore...
while (openList is not empty) {
    # pick one node to visit
    node = remove one item from openList
    
    # do something with this node (problem-specific)
    visit(node)
    
    # add it to the closed list to indicate "we've been there"
    closedList.add(node)
    
    # add all of the node's children to the open list, as long as we haven't already visisted them
    for (child in node.children) {
        if (closedList does not containc child) {
             openList.add(child)
        }
    } 
}

# when we break out of the loop we will have visited every node that is reachable from the starting node