STMicroelectronics Developer Interview Questions and Answers

Round duration - 75 minutes
Round difficulty - Medium

This was an online coding round where I had 2 questions to solve under 75 minutes. Both the coding questions were of Medium to Hard level of difficulty.

Q1. 
Smallest Window Problem Statement
Given two strings, S and X, your task is to find the smallest substring in S that contains all the characters present in X.
Example:
Input:
S = "abdd"
X = "bd"
Output:
...read more
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Q2. 
K - Sum Path In A Binary Tree
Given a binary tree where each node contains an integer value, and a value 'K', your task is to find all the paths in the binary tree such that the sum of the node values in ...read more
Ans. 
Find all paths in a binary tree where the sum of node values equals a given value 'K'.
• Traverse the binary tree using DFS and keep track of the current path and its sum.

• At each node, check if the current sum equals 'K' and add the path to the result.

• Continue traversal to the left and right child nodes recursively.

• Return the list of paths that sum up to 'K'.
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Round duration - 60 Minutes
Round difficulty - Medium

This round had 2 questions of DS/Algo to solve under 60 minutes and 2 questions related to Operating Systems.

Q1. 
Validate Partial Binary Search Tree (BST) Problem Statement
You are provided with a binary tree containing 'N' nodes. Your task is to determine if this tree is a Partial Binary Search Tree (BST). Return t...read more
Ans. 
Validate if a binary tree is a Partial Binary Search Tree (BST) by checking if each node's left subtree contains nodes with data less than or equal to the node's data, and each node's right subtree contains nodes with data greater than or equal to the node's data.
• Check if each node's left subtree follows BST property (data <= node's data) and right subtree follows BST property (data >= node's data)

• Recursively che...read more
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Q2. 
Longest Increasing Subsequence Problem Statement
Given an array of integers with 'N' elements, determine the length of the longest subsequence where each element is greater than the previous element. This...read more
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Q3. Can you define process and threads in operating systems?
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Q4. What are the different types of semaphores?
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Round duration - 60 Minutes
Round difficulty - Hard

In this round, I was asked 3 coding questions out of which I had to implement the first two and for the last question I was only asked the optimal approach. The main challenge in this round was to implement the first two questions in a production ready manner without any bugs and so I had to spent some time thinking about some Edge Cases which were important with respect to the question.

Q1. 
Next Greater Element Problem Statement
You are given an array arr of length N. For each element in the array, find the next greater element (NGE) that appears to the right. If there is no such greater ele...read more
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Q2. 
Power Set Generation
Given a sorted array of 'N' integers, your task is to generate the power set for this array. Each subset of this power set should be individually sorted.
A power set of a set 'ARR' i...read more
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Q3. 
Counting Sort Problem Statement
Ninja is learning about sorting algorithms, specifically those that do not rely on comparisons. Can you help Ninja implement the counting sort algorithm?
Example:
Input:
...read more
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Round duration - 75 minutes
Round difficulty - Medium

This was an online coding round where I had 2 questions to solve under 75 minutes. Both the coding questions were related to DP and were of Medium to Hard level of difficulty.

Q1. 
Longest Common Prime Subsequence Problem Statement
Imagine Ninja is tackling a puzzle during his long summer vacation. He has two arrays of integers, each with lengths 'N' and 'M'. Ninja's task is to dete...read more
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Q2. 
Maximum Sum Problem Statement
You are given an array ARR of N integers. Your task is to perform operations on this array until it becomes empty, and maximize the sum of selected elements. In each operatio...read more
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Round duration - 60 minutes
Round difficulty - Medium

This round had 2 Algorithmic questions wherein I was supposed to code both the problems after discussing their approaches and respective time and space complexities . After that , I was grilled on some OOPS concepts related to C++.

Q1. 
Cycle Detection in a Linked List
Your task is to determine if a given Singly Linked List of integers forms a cycle.
Explanation: A cycle in a linked list occurs when there is a node in the list that conn...read more
Ans. 
Detect if a given singly linked list of integers forms a cycle.
• Use Floyd's Tortoise and Hare algorithm to detect cycle in linked list

• Maintain two pointers, one moving at double the speed of the other

• If they meet at some point, there is a cycle in the linked list
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Q2. 
Check If Preorder Traversal Is Valid
Determine whether a given array ARR of positive integers is a valid Preorder Traversal of a Binary Search Tree (BST).
A binary search tree (BST) is a tree structure w...read more
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Q3. What are Vtable and VPTR in C++?
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Q4. What are friend functions in C++?
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Round duration - 60 minutes
Round difficulty - Medium

This was also a DS/Algo round where I was given 2 questions to solve and I was expected to come up with the optimal approach as far as possible. I solved both the questions with the optimal time and space complexities and then I was asked some more questions related to DBMS towards the end of the interview.

Q1. 
Top View of a Binary Tree
You are given a binary tree. Your task is to print the Top View of the Binary Tree, displaying the nodes from left to right order.
Input:
The first line contains an integer 't'...read more
Ans. 
The task is to print the Top View of a Binary Tree from left to right order.
• Use a map to store the horizontal distance of each node from the root.

• Perform a level order traversal of the tree and keep track of the horizontal distance of each node.

• Print the nodes in the map in ascending order of their horizontal distance.

• Handle the case where multiple nodes have the same horizontal distance by printing the one that appear...read more
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Q2. 
Count Palindromic Substrings Problem Statement
Given a string STR, determine the total number of palindromic substrings within STR.
Input:
The first line contains an integer 't' representing the number ...read more
Ans. 
Count the total number of palindromic substrings in a given string.
• Iterate through each character in the string and expand around it to find palindromic substrings.

• Use dynamic programming to store previously calculated palindromic substrings.

• Consider both odd and even length palindromes while counting.

• Example: For input 'abbc', palindromic substrings are ['a', 'b', 'b', 'c', 'bb']. Total count is 5.
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Q3. What is the difference between the DELETE and TRUNCATE commands in a DBMS?
Ans. 
DELETE removes specific rows from a table, while TRUNCATE removes all rows and resets auto-increment values.
• DELETE is a DML command, while TRUNCATE is a DDL command.

• DELETE can be rolled back, while TRUNCATE cannot be rolled back.

• DELETE triggers delete triggers, while TRUNCATE does not trigger any triggers.

• DELETE is slower as it maintains logs, while TRUNCATE is faster as it does not maintain logs.

• Example: DELETE FROM t...read more
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Q4. What is meant by normalization and denormalization?
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Medium coding qs with technical interview

Q1. Reverse an array
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