Charles Schwab Software Developer Intern Interview Questions and Answers

The questiona all are from aptitude

Some technical medium range questions asked

Q1. Main questions are from data structure
Add your answer
Q2. Some questions are from java
Add your answer
Q3. Some personal questions
Add your answer

Aptitude along with English and comprehensive questions

Three coding questions one easy one medium one hard

Q1. Binary Search question from leetcode
Add your answer
Q2. Merge sort code
Add your answer

Round duration - 135 minutes
Round difficulty - Hard

The Technical Round was of 2 hours 15 minutes and was conducted on HackerRank. It comprised of 5 sections:
Programming – 30 minutes: 2 easy to medium level questions (1 of 20 marks other of 30).
Quantitative Aptitude – 25 minutes: 7 Math-related MCQs.
Computer Science – 20 minutes: 8 MCQs based on Computer Science subject topics like OOPs, OS, DBMS, DSA 
Advanced Programming – 45 minutes: 1 question on advanced Data Structures (100 marks)
Tell me about Yourself – 15 minutes: 2 essay type questions

Q1. 
Counting Pairs Problem Statement
Given a positive integer N, determine the count of all possible positive integral pairs (X, Y) that satisfy the equation 1/X + 1/Y = 1/N.
Example:
Input:
T = 1
N = 2
Ou...read more
Ans. Naive Solution (Time limit Exceed)
• Given equation can be simplified as follows:
  • 1/X + 1/Y = 1/N
  • 1/X = 1/N - 1/Y
  • 1/X = (Y - N)/(N*Y)
  • X = (N*Y)/(Y - N)
  • X = (N*Y - N*N + N*N)/(Y-N)
  • X = (N(Y-N) + N*N)/(Y-N)
  • X = N + (N*N)/(Y-N)
• To identify the total number of pairs satisfying the given equation, iterate over all the possible values of X and Y and increment a counter, where current X and Y values satisfy the above equation.
• This will ...read more
Answered Anonymously
Add your answer
Q2. 
Level Order Traversal Problem Statement
Given a binary tree of integers, return the level order traversal of the binary tree.
Input:
The first line contains an integer 'T', representing the number of te...read more
Ans. Breadth First Search
In the level order traversal, we will be using queue data structure which has the property FIRST IN FIRST OUT that’s why which nodes come first in current level the children of that node will also come first for the next level. So, we visit all the nodes one by one of the current level and push into the queue so that when we will be complete with the current level, then we can start exploring nodes ...read more
Answered Anonymously
Add your answer
Q3. 
Maximize Matrix Binary Score
You are provided with a 2-D matrix called MAT consisting solely of 0s and 1s. Each row of the matrix can be viewed as a binary number, and the aggregate sum of these binary nu...read more
Ans. Brute Force
The idea is to use the properties of binary numbers to implement the solution in a brute force manner.
We know that the maximum number of 1s in a binary number will help in increasing the overall sum if they are as left as possible. One important observation that arises from this fact is that the first bit(extreme left) should be made 1 to maximize the number as 4(100) > 3(011). So, if the first column in ...read more
Answered Anonymously
Add your answer

Round duration - 11 hours
Round difficulty - Easy

Finally, I was selected for the interview round which was conducted virtually over zoom.I had 4 rounds spanning over a period of almost 11 hours (10 AM- 9 PM) with breaks in between rounds, of course. As each of these rounds was an elimination round candidate had 1 to 4 rounds. In the end, we were 13 students left out of 65 students.

Q1. 
Regular Expression Match Problem Statement
Given a string str and a string pat, where str may contain wildcard characters '?' and '*'.
If a character is '?', it can be replaced with any single character....read more
Ans. Recursion Based Approach
The idea is pretty straightforward: scan ‘str’ and ‘pat’ while there is a match between the current character of ‘str’ and the current character of ‘pat’. If we reach the end of both strings while there is still a match, return True, otherwise, return False. The scan is done by having a pointer ‘i’ in ‘str’ and a pointer ‘j’ in ‘pat'
 
Example: = "code"
 
The character 'c' of 'str matches ...read more
Answered Anonymously
Add your answer
Q2. 
Fastest Horse Problem Statement
Given ‘N’ horses running in separate lanes, each horse's finish time is provided in an array. You are tasked to process 'Q' queries. For each query, determine the time take...read more
Ans. Brute Force
For each query, we can simply loop between ‘L’ and ‘R’ and store the minimum time taken by a horse to complete the race in a variable, and return the value stored in that variable.
 
Algorithm for Each Query:
 
• Store the minimum time to complete the race in a variable ‘MINIMUMTIME’ and initialize it with a large enough number, in this case, 10^ 9 is sufficient.
• Iterate from ‘L’ to ‘R’ and if the time ta...read more
Answered Anonymously
Add your answer
Q3. 
Group Anagrams Together
Given an array/list of strings STR_LIST, group the anagrams together and return each group as a list of strings. Each group must contain strings that are anagrams of each other.
E...read more
Ans. Sorting based Approach
The idea behind this approach is that two or more than two strings are anagrams if and only if their sorted strings are equal. So we will use a HashMap, let’s say “anagramGroup”, where each key is a sorted string, and the key will be mapping to the list of indices from the given list of strings that form a group of anagrams. This means that if we sort the strings at those indices, we will get the ...read more
Answered Anonymously
Add your answer

Round duration - 90 minutes
Round difficulty - Hard

Timing was 10 AM. Environment was very well. Questions were well explained.

Q1. 
Minimum Umbrellas Problem
You are provided with ‘N’ types of umbrellas, where each umbrella type can shelter a certain number of people. Given an array UMBRELLA that indicates the number of people each um...read more
Ans. Brute Force
Approach: The idea here is to try every possible option and consider the minimum ans.

 We have two possible options: either we use the i-th umbrella to cover people or not. 

So, the recurrence for the above problem is:
minNumberOfUmbrellas(i, M) = min(minNumberOfUmbrellas(i - 1, M), 1+ minNumberOfUmbrellas(i, M - UMBRELLA[i])).
 
minNumberOfUmbrellas(i, M) represents the minimum number of umbrellas...read more
Answered Anonymously
Add your answer
Q2. 
Candies Distribution Problem Statement
Prateek is a kindergarten teacher with a mission to distribute candies to students based on their performance. Each student must get at least one candy, and if two s...read more
Ans. Brute Force
There can be four cases :
 
CASE 1: STUDENTS[i - 1]  > STUDENTS[i]  < STUDENTS[i + 1]
CASE 2: STUDENTS[i - 1]  < STUDENTS[i]  < STUDENTS[i + 1]
CASE 3: STUDENTS[i - 1]  > STUDENTS[i]  > STUDENTS[i + 1]
CASE 4: STUDENTS[i - 1]  < STUDENTS[i]  > STUDENTS[i + 1]
 
1. For case 1, the ‘i’th child will get one candy.
2. For case 2, the ‘i’th child will ge...read more
Answered Anonymously
Add your answer

Round duration - 90 minutes
Round difficulty - Hard

Timing was 10 AM. Environment was very well. Questions were well explained.

Q1. 
Minimum Umbrellas Problem
You are provided with ‘N’ types of umbrellas, where each umbrella type can shelter a certain number of people. Given an array UMBRELLA that indicates the number of people each um...read more
Ans. Brute Force
Approach: The idea here is to try every possible option and consider the minimum ans.

 We have two possible options: either we use the i-th umbrella to cover people or not. 

So, the recurrence for the above problem is:
minNumberOfUmbrellas(i, M) = min(minNumberOfUmbrellas(i - 1, M), 1+ minNumberOfUmbrellas(i, M - UMBRELLA[i])).
 
minNumberOfUmbrellas(i, M) represents the minimum number of umbrellas...read more
Answered Anonymously
Add your answer
Q2. 
Minimum Number of Swaps to Sort an Array
Find the minimum number of swaps required to sort a given array of distinct elements in ascending order.
Input:
T (number of test cases)
For each test case:
N (siz...read more
Ans. Naive Approach
While iterating over the array, check the current element, and if not in the correct place, replace that element with the index of the element which should have come in this place.
 
Below is the algorithm:
1. Create a copy of the given input array and store it in temp.
2. Sort the temp array.
3. Iterate over the input array, and check whether the current element is at the right place or not by comparing it with t...read more
Answered Anonymously
Add your answer

Round duration - 120 minutes
Round difficulty - Easy

This round was held in the evening at 6 o'clock on Hackerrank. It had coding questions: easy, medium, and hard level and MCQ's ( 1 minute for each MCQ). Negative marking was also there

Q1. 
Excel Column Number Problem Statement
Given a column title as it appears in an Excel sheet, return its corresponding column number.
Example:
Input:
"AB"
Output:
28
Explanation:
Column title "AB" co...read more
Add your answer
Q2. 
Climbing the Leaderboard Problem Statement
In a game leaderboard, scores determine rankings where the highest score gets rank 1. Players with identical scores share the same rank, followed by the next ran...read more
Add your answer

Round duration - 30 minutes
Round difficulty - Easy

This was an interview round ( technical round) that was held on video-call and a coding platform was also shared. The interviewer was very friendly with me . She was praising me on every solution that I provided.

Q1. 
Flatten The Multi-Level Linked List
You are given a multi-level linked list of N nodes, where each node can have two pointers: next and child. Flatten this multi-level linked list into a singly linked lis...read more
Add your answer
Q2. 
The Celebrity Problem
Imagine there are 'N' people at a party, each assigned a unique ID from 0 to N-1. A celebrity at the party is a person who is known by everyone but knows no one else.
Problem Statem...read more
Add your answer

Round duration - 35 minutes
Round difficulty - Easy

This was an interview round ( technical round) that was held on video-call and a coding platform was also shared. The interviewer was very friendly with me . She was praising me on every solution that I provided.

Q1. 
Design a HashSet
Create a HashSet data structure without using any built-in hash table libraries.
Functions Description:
1) Constructor: Initializes the data members as required.

2) add(value): Inserts...read more
Add your answer

Round duration - 20 minutes
Round difficulty - Easy

Online HR+Technical Round .

Round duration - 90 minutes
Round difficulty - Medium

It was on done in hackerrank

Q1. 
Matrix Rank Calculation
Given a matrix ARR of dimensions N * M, your task is to determine the rank of the matrix ARR.
Explanation:
The rank of a matrix is defined as:
(a) The maximum number of linearly...read more
Add your answer
Q2. 
Number of Triangles in an Undirected Graph
Determine how many triangles exist in an undirected graph. A triangle is defined as a cyclic path of length three that begins and ends at the same vertex.
Input...read more
Add your answer

Round duration - 20 minutes
Round difficulty - Medium

Interviewer was quite friendly