SDE - 1

Step 1 : Figure out how the tree will look after traversal and got the point that I have to do something like vertical order traversal
Step 2 : I do a level order traversal so that the topmost node at a horizontal node is visited before any other node of the same horizontal distance below it.
Step 3 : Hashing is used to check whether a node at a given horizontal distance is seen. 
Step 4 : I explained the whole approach and code

Step 1 : Initially I read the problem and start thinking about two pointer approach
Step 2 : But after a few minutes I got to the point where I can treat balls as numbers (i.e 0, 1, 2) then I remembered the DNF algorithm
Step 3 : So I took three-pointers i.e low, high, and mid, and write code keeping in mind I save to store red -> white -> blue and applied DNF algo

Step 1 : He just asked for an approach to this question so I told him like that
Consider each cell as a node and each boundary between any two adjacent cells be an edge. so the total number of Nodes is N * N. So the idea is to do a breadth-first search from the starting cell till the ending cell is found.
Step 2 : Then he asked for time complexity

Tip 1 : Practice SQL queries 
Tip 2 : Grasp theoretical concepts also

Tip 1 : Practice the design of the schema
Tip 2 : Well understanding of the keys in schema