Tata Consultancy Services (TCS) Interview Guide

Approach: Define each: Encapsulation, Inheritance, Polymorphism, Abstraction. Give one real-world example for each.

Approach: Overloading = same name, different parameters (compile-time). Overriding = same signature in parent-child (runtime).

Approach: Occurs in multiple inheritance when two parent classes have the same method. Explain how Java solves it with interfaces.

Approach: Virtual functions enable runtime polymorphism. Vtable is a lookup table of function pointers created at compile time.

Approach: Self-join: SELECT e.name FROM emp e JOIN emp m ON e.manager_id = m.id WHERE e.salary > m.salary

Approach: Index is a data structure (B-tree) that speeds up data retrieval. Explain trade-off with insert/update performance.

Approach: Atomicity (all or nothing), Consistency (valid states), Isolation (concurrent transactions), Durability (permanent).

Approach: DELETE = row-by-row (can rollback), TRUNCATE = all rows (cannot rollback), DROP = removes table structure.

Approach: Iterative: three pointers (prev, curr, next). Recursive: reverse rest of list, then adjust pointers.

Approach: Use in-order traversal (should be sorted) or validate with min/max bounds at each node.

Approach: Push: enqueue to Q1. Pop: dequeue all except last from Q1 to Q2, return last, swap Q1 and Q2.

Approach: Use min-heap of size k, or QuickSelect algorithm for O(n) average case.