Perfios Software Solutions Senior Technical Team Member Interview Questions and Answers

Rotate an array of strings by n positions

• Create a new array and copy elements from original array starting from index n to the end, then copy elements from index 0 to n-1

• Alternatively, you can use array slicing to achieve the rotation

• Example: Original array ['a', 'b', 'c', 'd', 'e'], rotate by 2 positions would result in ['c', 'd', 'e', 'a', 'b']

Use ORDER BY and LIMIT to get last entry in SQL query

• Use ORDER BY column_name DESC to sort in descending order

• Use LIMIT 1 to get only the last entry

Hash map is a data structure that stores key-value pairs and uses a hash function to map keys to their corresponding values.

• Hash map uses a hash function to determine the index of the key-value pair in the underlying array.

• Collisions can occur when two keys hash to the same index, which can be resolved using techniques like chaining or open addressing.

• Hash maps offer constant time complexity O(1) for insertion, deletio...read more

Implementing a palindrome check in Java without using the reverse() function.

• Create a function that takes a string as input.

• Use two pointers, one starting from the beginning of the string and the other from the end.

• Compare characters at the two pointers and move them towards each other until they meet or cross.

• If all characters match, the string is a palindrome.

• Example: 'racecar' is a palindrome.

• Example: 'hello' is not...read more

Use counting method to sort array of strings with 0's and 1's.

• Create a count array to store the frequency of 0's and 1's.

• Update the original array based on the count array.

• Example: Input array - ['0', '1', '0', '1', '1'], Output array - ['0', '0', '1', '1', '1']

HTTPS provides secure communication over the internet using encryption, while HTTP does not.

• HTTPS uses SSL/TLS encryption to secure data transmission, while HTTP does not.

• HTTPS URLs begin with 'https://' and use port 443, while HTTP URLs begin with 'http://' and use port 80.

• HTTPS ensures data integrity and authentication, while HTTP does not provide these security measures.

The algorithm to reverse a singly linked list involves iterating through the list and changing the pointers to reverse the direction of the links.

• Start with three pointers: current, previous, and next.

• Iterate through the list, updating the next pointer to point to the previous node.

• Move the previous pointer to the current node and the current pointer to the next node.

• Continue until the end of the list is reached, then ...read more

SQL query to retrieve data from employee table

• Use SELECT statement to retrieve data

• Specify the columns you want to retrieve

• Use FROM clause to specify the table name

• Add any conditions using WHERE clause if needed