UBS C Developer Interview Questions, Process, and Tips

Round duration - 120 minutes
Round difficulty - Easy

2 coding questions and 10 MCQ based on find output of code and some aptitude.

Q1. 
String Transformation Problem
Given a string (STR) of length N, you are tasked to create a new string through the following method:
Select the smallest character from the first K characters of STR, remov...read more
Ans. Brute Force Approach
• Create a new “answer” string that will contain the modified string
• While the input string's length is greater than 0
  • Find the minimum character in the first K characters of the string (or the entire string if its length is less than K)
  • Append that character to the “answer” string
  • Remove that character from the input string
• Return the “answer” string
Space Complexity: O(1)Explanation:
O(1)
 
Since we ar...read more
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Q2. 
Find Maximum Number by At-most K Swaps
Given an array of non-negative integers representing the digits of a number and an integer 'K', calculate the maximum possible number by swapping its digits up to 'K...read more
Ans. Brute Force
The idea is to generate all the possible numbers by trying all the possible combinations of indices at most ‘K’ times. We will do this task with a recursive function and each time we swap two indices we will decrease the value of ‘K’ by 1. So base case is when ‘K’ is equal to zero and each time when we swap indices we will check whether the current number is the maximum possible or not.
 
Here is the algo...read more
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Round duration - 45 minutes
Round difficulty - Easy

C++ questions, one coding question, some python question

Q1. 
Merge K Sorted Arrays Problem Statement
Given 'K' different arrays that are individually sorted in ascending order, merge all these arrays into a single array that is also sorted in ascending order.
Inpu...read more
Ans. Sorting
 
1. Create an output array ‘RESULT’.
2. Traverse all the given arrays from start to end and insert all the elements in the output array ‘RESULT’.
3. Sort the ‘RESULT’ and return it.
Space Complexity: O(2^n)Explanation:
O(N * K), Where ‘K’ is the number of arrays and ‘N’ is the average number of elements in every array.
 
We are using an array/list of size O(N * K) to store all the elements of the ‘K’ arrays/lists. T...read more
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Round duration - 45 minutes
Round difficulty - Easy

C++ related questions, coding questions, past internship experience,some python questions

Q1. 
Sort 0 1 2 Problem Statement
Given an integer array arr of size 'N' containing only 0s, 1s, and 2s, write an algorithm to sort the array.
Input:
The first line contains an integer 'T' representing the n...read more
Ans. Sorting
Use any good sorting algorithm like Merge Sort, Quick Sort or inbuilt sorting function of different languages.
• Sort the Array and just return.
Space Complexity: O(1)Explanation:
O(1), As we are using constant space.
Time Complexity: O(nlogn)Explanation:
O(N*log(N)), where ‘N’ is the size of the array.
We are using inbuilt sort algorithm which has Overall Time Complexity O(N*log(N))
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Q2. 
Move Zeroes to End Problem Statement
Given an unsorted array of integers, modify the array such that all the zeroes are moved to the end, while maintaining the order of non-zero elements as they appear or...read more
Ans. Naive Approach
Hint: can you think of separating zero elements and non-zero elements in different containers?

 
Approach : 

 
We can create a new array of integers. As soon as we find a non-zero element, we can directly insert it into our new array. After that, we can insert all the left zero’s. 

 
We can easily calculate the number of left zeroes as : 
 
Size of original array = size of new a...read more
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Round duration - 60 minutes
Round difficulty - Medium

Data Structure questions, trees questions.

Q1. 
Preorder Traversal of a BST Problem Statement
Given an array PREORDER representing the preorder traversal of a Binary Search Tree (BST) with N nodes, construct the original BST.
Each element in the given...read more
Ans. Brute Force Approach
We have a simple Brute Force solution for this problem. We will traverse the PREORDER array, find the left subtree and right subtree and then recursively construct the tree as follows-
 
• The first element of the preorder traversal corresponds to the root of BST.
• We will find the index ‘SPLIT’ of the first element in the given traversal which is greater than the root node i.e PREORDER[‘SPLIT’] >...read more
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Q2. 
BST Node Deletion Problem
Given a binary search tree (BST) and a key value K, your task is to delete the node with value K. It is guaranteed that a node with value K exists in the BST.
Explanation:
A bi...read more
Ans. Recursive Solution - 1
• There can be three cases when a node is to be deleted:
  • The node has 0 children/ node is a leaf. In this case, simply remove the node from the tree.
  • The node has 1 child. In this case, delete the node and copy the child to this node.
  • The node has 2 children. In this case, delete the node and copy the inorder successor to this node. (You could have also used the inorder predecessor).
• To find the inorder...read more
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