60+ Semco Maritime Interview Questions and Answers

Right outer join is a type of join operation that returns all the rows from the right table and the matching rows from the left table.

• Right outer join is denoted by the RIGHT JOIN keyword in SQL.

• It is used to combine rows from two tables based on a related column.

• In the result set, unmatched rows from the right table will have NULL values for the columns of the left table.

• A real-world scenario for using a right outer join is when analyzing customer data and sales data. The ri...read more

Convert string to integer without using inbuilt function

• Iterate through each character and multiply by 10 and add the integer value of the character

• Use ASCII values to convert character to integer

• Handle negative numbers separately

Recursion is a process in which a function calls itself repeatedly until a base condition is met.

• Recursion involves breaking down a problem into smaller subproblems and solving them recursively.

• It uses a stack to keep track of function calls and their parameters.

• Examples include factorial, Fibonacci sequence, and binary search.

• Compiler executes recursion by allocating memory for each function call and storing the return address and local variables on the stack.

• It then pops th...read more

Python is a high-level programming language known for its simplicity and readability. Constructors are special methods used to initialize objects in classes.

• Python is a versatile programming language used for web development, data analysis, artificial intelligence, and more.

• Constructors in Python are special methods with the __init__() function that initialize objects when they are created.

• Arrays in Python are data structures that can hold multiple values of the same type. Th...read more

Swapping two character variables without using third

• Use XOR operator to swap two variables without using third variable

• Assign the XOR of both variables to the first variable

• Assign the XOR of the first variable and second variable to the second variable

A program demonstrating recursion using factorial function.

• Recursion is a technique where a function calls itself.

• Factorial function is a classic example of recursion.

• Each recursive call creates a new stack frame.

• The base case is when the input is 1, and the function returns 1.

• The final result is the product of all the recursive calls.

• Example: factorial(5) = 5 * factorial(4) = 5 * 4 * factorial(3) = ... = 5 * 4 * 3 * 2 * 1 = 120.

Primary key uniquely identifies a record in a table, while Unique key ensures uniqueness of a column.

• Primary key can't have null values, Unique key can have one null value

• A table can have only one Primary key, but multiple Unique keys

• Primary key is automatically indexed, Unique key is not necessarily indexed

The data structure used in recursion is a stack.

• Recursion uses a stack data structure to keep track of function calls.

• Each time a function is called, its parameters and local variables are pushed onto the stack.

• When the function returns, the values are popped off the stack.

• This allows the program to keep track of where it is in the recursive process.

• Examples of recursive algorithms that use a stack include depth-first search and quicksort.

Program to check if a string is a palindrome or not.

• Remove all spaces and convert to lowercase for case-insensitive comparison.

• Compare the first and last characters, then move towards the center until all characters have been compared.

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

• If any characters do not match, the string is not a palindrome.

A friend function is a non-member function that has access to the private and protected members of a class.

• Declared inside the class but defined outside the class scope

• Can access private and protected members of the class

• Not a member of the class but has access to its private members

• Used to allow external functions to access and modify private data of a class

• Can be declared as a friend in another class

Garbage collection in Java is an automatic memory management process.

• It frees up memory by removing objects that are no longer in use.

• It is performed by the JVM in the background.

• It helps prevent memory leaks and improves performance.

• There are different types of garbage collectors in Java, such as Serial, Parallel, CMS, and G1.

• Example: int[] arr = new int[1000]; arr = null; // Garbage collector will remove the array from memory

Addition and Deletion of a node in binary tree

• For addition, traverse the tree to find the appropriate position and add the new node as a leaf

• For deletion, find the node to be deleted and replace it with its successor or predecessor

• In case of deletion, if the node has two children, find the inorder successor and replace it with the node to be deleted

atoi function converts a string to an integer in C.

• The function takes a string as input and returns an integer.

• Leading white spaces are ignored.

• If the string contains non-numeric characters, the function stops conversion and returns the converted value.

• The function returns 0 if the input string is not a valid integer.

• Example: atoi('123') returns 123.

A program to print star pattern

• Use nested loops to print the pattern

• The outer loop controls the number of rows

• The inner loop controls the number of stars to be printed in each row

• Use print() or println() function to print the stars

Refrential integrity ensures that relationships between tables in a database remain consistent.

• It is a database concept that ensures that foreign key values in one table match the primary key values in another table.

• It prevents orphaned records in a database.

• It maintains data consistency and accuracy.

• For example, if a customer record is deleted, all related orders for that customer should also be deleted.

• It is enforced through constraints such as foreign key constraints.

Singleton pattern is a design pattern that restricts the instantiation of a class to one object.

• Used when only one instance of a class is needed throughout the application

• Provides a global point of access to the instance

• Implemented using a private constructor and a static method to return the instance

• Example: Database connection, Logger, Configuration settings

Data structures are used to organize and store data in a computer program.

• Arrays - used to store a collection of elements of the same data type

• Linked Lists - used to store a collection of elements where each element points to the next element

• Stacks - used to store a collection of elements where the last element added is the first element removed

• Queues - used to store a collection of elements where the first element added is the first element removed

• Trees - used to store hiera...read more

I know multiple programming languages including Java, Python, and C++.

• Java

• Python

• C++

Static variable is a variable that retains its value even after the function execution is completed.

• Declared with static keyword

• Memory is allocated once and shared among all instances of the class or function

• Can be accessed without creating an object of the class

Triggers are database objects that are automatically executed in response to certain events.

• Triggers can be used to enforce business rules, audit changes, or replicate data.

• There are two types of triggers: DML triggers and DDL triggers.

• DML triggers are fired in response to DML statements (INSERT, UPDATE, DELETE).

• DDL triggers are fired in response to DDL statements (CREATE, ALTER, DROP).

Libraries and packages in Python are reusable collections of code that provide functionality to perform specific tasks.

• Libraries and packages help in reducing the amount of code that needs to be written from scratch

• Popular libraries in Python include NumPy for numerical computing, Pandas for data manipulation, and Matplotlib for data visualization

• Packages can be installed using package managers like pip or conda

Run time polymorphism is the ability of a program to determine the object type at runtime and call the appropriate method.

• It is achieved through virtual functions and dynamic binding.

• Allows for more flexible and extensible code.

• Example: a base class Animal with virtual function makeSound() and derived classes Dog and Cat that override makeSound().

• At runtime, if an Animal pointer points to a Dog object, calling makeSound() will execute the Dog's implementation.

Five commonly used Linux commands

• ls - list directory contents

• cd - change directory

• mkdir - make directory

• rm - remove files or directories

• grep - search for a pattern in a file

Query for deleting data from a database table.

• Use the DELETE statement followed by the table name.

• Add a WHERE clause to specify the condition for deleting specific rows.

• Be careful when deleting data as it cannot be recovered.

• Example: DELETE FROM customers WHERE customer_id = 1234;

Time complexity refers to the amount of time taken by an algorithm to run as the input size increases.

• It measures the efficiency of an algorithm.

• It is usually expressed in Big O notation.

• An algorithm with a lower time complexity is more efficient than one with a higher time complexity.

Count the number of vowels in a given string

• Iterate through each character in the string and check if it is a vowel (a, e, i, o, u)

• Maintain a count of vowels encountered

• Return the total count of vowels in the string

A copy constructor is a special type of constructor which creates a new object as a copy of an existing object.

• Ensure the copy constructor has the same signature as the default constructor.

• Allocate memory for the new object and copy the values from the existing object.

• Handle deep copy vs shallow copy based on the object's data types.

A copy constructor is a special type of constructor in object-oriented programming that creates a new object as a copy of an existing object.

• Creates a new object by copying the attributes of an existing object

• Used to initialize a new object with the values of an existing object

• Helps in creating deep copies of objects to avoid shallow copy issues

Object-oriented programming paradigm in Java focusing on objects and classes.

• OOPs stands for Object-Oriented Programming.

• It focuses on creating objects that interact with each other through classes.

• Key principles include Inheritance, Encapsulation, Polymorphism, and Abstraction.

• Example: Class Car { String color; void start() { //code here } }

• Example: Car myCar = new Car(); myCar.color = 'red'; myCar.start();

Collection framework in Java provides a set of interfaces and classes to store and manipulate groups of objects.

• Includes interfaces like List, Set, and Map

• Classes like ArrayList, LinkedList, HashSet, and HashMap implement these interfaces

• Provides methods for adding, removing, and accessing elements in collections

Count the number of occurrences of a specific substring in an array of strings.

• Iterate through each string in the array and use a function to count occurrences of the substring.

• Use a loop to go through each character in the string and check for matches with the substring.

• Keep a count variable to track the number of occurrences found.

Joins are used in databases to combine rows from two or more tables based on a related column between them.

• Joins are used to retrieve data from multiple tables based on a related column.

• Common types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.

• INNER JOIN returns rows when there is at least one match in both tables.

• LEFT JOIN returns all rows from the left table and the matched rows from the right table.

• RIGHT JOIN returns all rows from the right table and t...read more