OpenXcell Technolabs PHP Developer Interview Questions and Answers

Validate if a binary tree is valid or not

• A valid binary tree should not have any duplicate nodes

• A valid binary tree should have all left nodes smaller than the parent node and all right nodes greater than the parent node

• We can use recursion to traverse the tree and check if it is valid

Reversing a linked list involves changing the direction of the pointers in the list.

• Iteratively swap the next and previous pointers of each node in the list

• Recursively swap the next and previous pointers of each node in the list

• Use a stack to push each node onto the stack and then pop them off in reverse order

• Create a new list and iterate through the original list, adding each node to the front of the new list