Classic Informatics Interview Questions and Answers

Complex SQL scenarios and their results

• Using subqueries to filter data

• Joining multiple tables with complex conditions

• Using window functions to calculate running totals

• Pivoting data to transform rows into columns

• Using recursive queries to traverse hierarchical data

Check if binary tree is balanced or not.

• A balanced binary tree has the height of left and right subtrees differ by at most 1.

• Recursively check the height of left and right subtrees and compare.

• Use a helper function to calculate the height of a subtree.

• Time complexity: O(nlogn) for a balanced tree, O(n^2) for a skewed tree.

Detect loops in a linked list.

• Use two pointers, one moving at a faster pace than the other.

• If there is a loop, the faster pointer will eventually catch up to the slower one.

• To detect the start of the loop, reset one pointer to the head and move both pointers at the same pace.