Detects if there is at least a cyclic path in all available routes

checkCyclicPath.java

public boolean isThereCycle(Map<Character, List<Character>> map){
        if(map == null || map.isEmpty()) return false;

        //use each node as starting point
        for(char item : map.keySet()){
            //create new tracking experience for each start point
           Stack<Character> trackPad = new Stack<>();
           List<Character> visitedPoints = new ArrayList<>();

           visitedPoints.add(item);
           trackPad.addAll(map.get(item));

            while(!trackPad.isEmpty()){
                char subItem = trackPad.pop();

                //check if subpath leads back to origin
                //if key is not found, return a default list - handles null exceptions
                if(map.getOrDefault(subItem, new ArrayList<>()).contains(item)) return true;

                //avoid re-processing a path
                if(!visitedPoints.contains(subItem)){
                    trackPad.addAll(map.getOrDefault(subItem, new ArrayList<>()));
                    visitedPoints.add(subItem);
                }

            }
        }
        return false;
    }

Hello @deedee47, thank you for participating in Week 9 of #AlgorithmFridays.

Your solution is clean, easy to read for the most part and passes some of the test cases. One test case it doesn't pass however is when there is a path leading out from a node back to itself.

Here is an example:

map = { 'A': ['A'] } # this should return true but yours returns false

In the above instance, there is a path leading from A back to A so it should return true. Is there a chance you made an assumption that this was not possible? Let me know what you think!

But in all, this was a good attempt and you demonstrated good knowledge of solving graph traversal problems and using the Stack data structure. Really neat!

Hi @meekgeek, true, I agree the use case is valid. Surprisingly it returns true when i debugged it with the example. Thanks for the feedback