Wave Visions Mobile and Web Application Developer Interview Questions and Answers

Queue can be implemented using two stacks by maintaining the order of elements in the stacks.

• Create two stacks, let's call them stack1 and stack2

• When an element is enqueued, push it to stack1

• When an element is dequeued, pop all elements from stack1 and push them to stack2

• Pop the top element from stack2 and return it as the dequeued element

• If stack2 is empty, repeat step 3

• To get the front element of the queue, peek the

Left join returns all records from left table and matching records from right table. Full outer join returns all records from both tables.

• Left join is used to combine two tables based on a common column.

• In left join, all records from the left table are returned along with matching records from the right table.

• If there is no match in the right table, NULL values are returned.

• Example: SELECT * FROM table1 LEFT JOIN table...read more

Magic functions are special methods in PHP that start with __. Autoloading is a way to automatically load classes.

• Magic functions are used to handle certain events in PHP, such as object creation or property access.

• Autoloading allows PHP to automatically load classes when they are needed, without requiring manual includes.

• Magic functions can be used in conjunction with autoloading to dynamically load classes or handle

Given three sorted arrays, find common elements.

• Create three pointers to traverse each array

• Compare the elements at the pointers and move the pointer of the smallest element

• If all pointers point to the same element, add it to the result and move all pointers

• Repeat until any pointer reaches the end of its array

Check if a number is a power of 2 or not.

• A power of 2 has only one bit set in its binary representation.

• Use bitwise AND operator to check if the number is a power of 2.

• If n is a power of 2, then n & (n-1) will be 0.

Event bubbling is the propagation of an event from the innermost child element to the outermost parent element.

• Events triggered on a child element will also trigger on its parent elements

• The event travels up the DOM tree until it reaches the document object

• Can be stopped using event.stopPropagation()

• Can be useful for event delegation

The .on('click',function() is a more flexible method than .click(function())

• The .on() method can handle multiple events and selectors

• The .click() method can only handle one event and one selector

• The .on() method can also handle dynamically added elements

• The .click() method cannot handle dynamically added elements

Function to check if two strings are anagram or not

• Create two character arrays from the strings

• Sort the arrays

• Compare the sorted arrays

Function to determine the order of integers in an array.

• Check first and last element to determine if increasing or decreasing

• Check for inflection point to determine if order changes

• Return order type as string

Optimize images, minify code, reduce HTTP requests, use caching, and lazy loading.

• Optimize images using compression and appropriate file formats

• Minify code to reduce file size and improve load times

• Reduce HTTP requests by combining files and using sprites

• Use caching to store frequently accessed data locally

• Implement lazy loading to defer loading of non-critical resources

Design a database schema for a movie site with user ratings and recommendations.

• Create tables for movies, users, ratings, and recommendations

• Use foreign keys to link tables

• Include columns for movie genre and user watch history

• Algorithm for recommendations can use user watch history and ratings to suggest similar movies

Function to simulate dice roll with equal probability without using random function

• Use a toss function that returns either 0 or 1 with equal probability

• Call the toss function 3 times and convert the result to a binary number

• If the binary number is greater than 0 and less than or equal to 6, return it

• If the binary number is greater than 6, repeat the process

Query to fetch duplicate email from table

• Use GROUP BY and HAVING clause to filter out duplicates

• SELECT email, COUNT(*) FROM table_name GROUP BY email HAVING COUNT(*) > 1;

• This will return all the duplicate emails in the table