Latest CoderPad Interview Questions to Prepare

CoderPad Interview Questions


CoderPad is an online coding tool that allows you to run your code on the go and is mainly used for conducting technical interviews. It is used both by employees and clients for testing and judging a person’s programming capabilities. A candidate should be well aware of Coderpad before taking an interview through it. You need to have good practice since it does not show suggestions, unlike other IDEs. Questions are mostly easy but twisted. CoderPad records your complete interview, which can be accessed later on. It also supports video calls using the “Start Call” button. So, in this article, we will discuss the CoderPad Interview Questions here.

CoderPad Interview Questions

Here are some sample questions which an interviewer can ask. It includes the main logic part of the problem you need to know to solve the complete problem.

  1. Make the largest possible numbers using all the numbers available in the matrix. For example, if the array is [1,61,9,0], the largest number formed will be 96110.

=> Many people’s 1st approach would be to sort the numbers in descending order. Though this will not work since 61 is bigger than 9 but comes after 9. Hence we need to compare two numbers using a comparison function. We need to compare AB and BA. If AB> BA, then we put AB else, we choose BA. 

Example: A=61, B=9, AB=619, BA=961 

Here we see that BA> AB, hence we choose BA.

By using this approach you can easily write code for this problem.

  1. Consider an array that has both positive and negative numbers. Then, write a program to find all pairs of numbers whose sum is equal to a number assigned manually( say given sum).

=>  Example: We have an array A=[1,2,3,4,5], given_sum=4 then the output will be 1 as only (1,3) pair is equal to 4. First, we need to 1st enter all numbers in an array and then take our desired sum to be checked. Then we need to check each pair of numbers using a loop condition. We will keep on updating it whenever we find a successful pair. In the end, we will print the output.

  1. Check a string for string segmentation using a given dictionary.

=> Example, Our Dictionary is {“cricket,” bat” } and input string is “batcricketcricket.” In this case, the output will be true since you can reuse a dictionary.

Algorithm for this problem:

  • n=length of input string
  • for a =0
  • first_word=substring (input string from index [0, a] )
  • second_word =substring (input string from index [a + 1, n – 1] )
  •  if dictionary has first_word
  •  if second_word is in dictionary OR second_word is of zero length, then return true
  •  Now recursively call this method with second_word as input and return true if it can be segmented 
  1. Find the missing number in an array from range 0 to n.

=> Example for {5,2,3,1,0} missing number is 4. There are many approaches to solve this problem. Though the below-mentioned method is the best.


  • Find the expected sum of the series using the Arithmetic Progression formula n*(n+1)/2
  • Now find the sum of all the numbers in the array.
  • Subtract the above-found sum from the expected sum. The difference will give us the answer. 
  1. Print a fibonacci series using recursion.

=> A fibonacci series is in the order 0,1,1,2,3,5,8,13,21,34,55,…

Where each appearing element is the sum of the previous two elements i.e c=a+b.

To print such a pattern using recursion, we need to call the method again and again. There will be the main function from which we will call the recursive function. Let us consider the recursive function is fibb().

//From main function

Int a=5;


// From fibb function

int fibb (int a)


If (a<=1) 


return a;




return fibb(a-1)+ fibb(a-2);



In this program, we will get the final output as 55.

  1. How will you check if a number is prime or not?

=> A number is said to be prime if it is divisible by the number and 1 only. 0 and 1 are prime numbers. To check for a number n, we can run a loop till n/2 and try to divide it by a number greater than 1 and less than n/2. If any number can divide it, then we will break and return “Not Prime.” Else we will print “Prime.”

  1. Find the longest common prefix from several strings stored in an array?

=> Example: We have an array ar={“sumprime,” “sumnum,” “sumodd,” “sumeven”} then the longest prefix would be “sum” as it is common in every string. 


  • We will first find the minimum String in the array
  • Then we will iterate the complete array and check it with the minimum String character by character. Whenever we find a mismatch, we will break the loop, and that index will give us the longest common prefix.
  1. Write a program to remove any character of your choice from a string completely.

=> Example in a string “This is Life” we want to remove f. We can do it with the help of user-defined functions in java.


  • User input a String s
  • Run a user defined function say charRemove(s,’f’)
  • charRemove(String s, char c) will save a string in a character array char t[]
  • Take count=0
  • for(int i=j=0; i<s.length(); i++)
  • if (t[i]!=c)
    • t[j++]=t[i]
  • else
    • count++;
  • Run a while loop
  • while (count>0)




  • print t
  1. Find the longest line in a file using Python language?

=> Python comes with many inbuilt functions and methods. Using file handling functions, we can easily write the programming part just in a couple of lines. First, save some text in a file. Then, save it with the name ‘test.txt.’

//Main command

print (max (open(‘test.txt’),key=len)) 

It will print the longest line existing in the test.txt using the Python program. Remember to save the text file in the same folder where your Python program is situated. If the file is saved at another location, then you need to give the complete path.

  1. Write a program to implement Bubble sort.

=> Bubble sort is a sorting technique used to arrange numbers in either ascending or descending order. It works by swapping the adjacent elements if they are wrongly placed.


  • Take an array a[] of n numbers as input to sort
  • for(int i=0; i<n-1; i++)
  • for(int j=0; j<n-i-1; j++)
  • If a[j] > a[j+1] 

Then swap a[j] with a[j+1]

This will sort the numbers in ascending order. If you want to sort the numbers in descending order, you can swap when the condition a[j]< a[j+1] holds.

  1. Swap two numbers without using a third variable?

=> This problem is actually not dependent on any programming skill. All you need is to have some logical thinking.

Suppose we have 2 variables x and y. Value of x=52 and y=67. Now we want to swap them without using a third variable. Then the code will be:

y=y+x; //Sum of both numbers

x=y-x;  // x is now swapped (previous value of y).

y= y-x; // y is now swapped (previous value of x).

Final Notes

CoderPad is an amazing tool for conducting coding interviews in today’s time. All you need to do is to have a good practice of coding along with programming languages syntax. Many people get afraid when they don’t get desired output. Always try to figure out why the error occurred. Try to analyze your output, and that would be enough to solve the problem in most cases.

Frequently Asked Questions

  • Do I need to pay to use CoderPad? CoderPad price depends upon its user. If you are a candidate, it is free for you, but you need to pay for it if you are an interviewer. It also comes with a 7 day-trial for someone who wants to test before subscribing to it.
  • What makes CoderPad different from other IDEs? Most IDEs are made to help its user in coding easily by giving them hints and suggestions. CoderPad is different since it does not offer suggestions to you.
  • How long is an interview stored? All interviews conducted through CoderPad are saved forever. You can access them anytime. It would include all details- code execution and output. 
  • How many languages are supported by CoderPad? CoderPad currently supports 30+ languages. It includes all the major languages, including Perl, PHP, Kotlin, Java, JavaScript, HTML/CSS/JS, Go, Dart, C++, C#, C, Vue JS, React JS, MySQL, etc.
  • How is the CoderPad interview conducted? It is conducted both in audio/video mode. There is a “Start Call” button in the bottom left corner for starting a video/audio code. It will ask you for permission if you are using it for the 1st time. After that, you can turn audio and video on/off depending on your need. All calls are hosted through Twilio.
  • What is the time limit for a CoderPad interview? Minimum 30 minutes, 1 hour, 90 minutes, 2 hours, 3 hours, or you have no time limit.
Latest CoderPad Interview Questions to Prepare

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