Linkedin Coding Round 1 (Horrible experience)

• Constructed a path from root to node.
• Reverse iterated the path and for each node:
  • Checked the whole subtree for a matching node.
  • Otherwise, checked the closest leaf in the alternate direction compared to the child direction for each parent node.

The candidate attempted to write the following code:

public class Linkedin {
    List<TreeNode> path;
    public int FindClosestLeaf(TreeNode root, int k) {
        GetPath(root, k, new List<TreeNode>());

        int minLeafDistance = 1001;
        minLeafDistance = Math.Min(minLeafDistance, getClosestLeafDist(path.Last()));

        for(int i=path.Count-2; i >= 0; i--){
            TreeNode current = path[i];
            TreeNode next = path[i+1];

            int dist = 1001;

            if(next == current.left && current.right != null){
                dist = getClosestLeafDist(current.right) + 1;
            } else if(next == current.right && current.left != null){
                dist = getClosestLeafDist(current.left) + 1;
            }

            minLeafDistance = Math.Min(minLeafDistance, dist + (path.Count-i-1));
        }
        return minLeafDistance;
    }

    private void GetPath(TreeNode root, int k, List<TreeNode> pth){
        if(root == null){
            return;
        }

        pth.Add(root);
        if(root.val == k){
            this.path = new List<TreeNode>(pth);
            return;
        }

        GetPath(root.left,k,pth);
        GetPath(root.right,k,pth);
        pth.RemoveAt(pth.Count-1);
    }

    private int getClosestLeafDist(TreeNode root){
        if(root == null || (root.left == null && root.right == null)){
            return 0;
        }

        if(root.left == null){
            return 1 + getClosestLeafDist(root.right);
        }

        if(root.right == null){
            return 1 + getClosestLeafDist(root.left);
        }

        return Math.Min(getClosestLeafDist(root.left), getClosestLeafDist(root.right)) + 1;
    }
}

The interviewer continuously pinpointed issues with the candidate's code, questioning the use of DFS over BFS, and highlighting potential null pointer exceptions. The candidate felt that the interviewer did not allow them to complete their reasoning and created an environment of stress with constant interruptions.