LG Soft India Interview Questions and Answers

Sort an array of 0s, 1s, and 2s in linear time complexity.

• Use three pointers to keep track of the positions of 0s, 1s, and 2s.

• Traverse the array and swap elements to their respective positions.

• Time complexity: O(n), Space complexity: O(1).

String is immutable in Java to ensure security, thread safety, and optimization.

• Immutable strings are thread-safe as they cannot be modified concurrently by multiple threads.

• String pooling allows Java to optimize memory usage by reusing common string literals.

• Immutable strings prevent security vulnerabilities like SQL injection attacks.

Abstract class is a class that cannot be instantiated, while an interface is a contract that a class must implement.

• Abstract classes can have implemented methods, while interfaces cannot

• A class can implement multiple interfaces, but can only inherit from one abstract class

• Interfaces are used for achieving multiple inheritance in Java

• Abstract classes are used for creating a base class for other classes to inherit from

• Example of abstract class: public abstract class Animal { pu...read more

Spiral order traversal of BST

• Use two stacks to traverse the tree in a spiral order

• Push the root node into the first stack

• While the first stack is not empty, pop a node and print its value

• Push its left and right children into the second stack

• Once the first stack is empty, swap the stacks and repeat the process

• Continue until both stacks are empty

Hashmap is a key-value pair data structure while Hashset is a set of unique values.

• Hashmap allows duplicate values but not duplicate keys.

• Hashset does not allow duplicate values.

• Hashmap is implemented using a combination of hash table and linked list.

• Hashset is implemented using only a hash table.

• Example of Hashmap: {1:'one', 2:'two', 3:'three'}

• Example of Hashset: {'apple', 'banana', 'orange'}