Mock Interview: Practice Session for Software Engineering Roles

How do you find the missing number in a given integer array of 1 to 100?

def find_missing_number(arr):
  expected_sum = sum(range(1, 101))
  actual_sum = sum(arr)
  return expected_sum - actual_sum

How do you check if a string contains only digits?

def contains_only_digits(s):
  return s.isdigit()

How would you check if two strings are anagrams?

from collections import Counter

def are_anagrams(str1, str2):
  return Counter(str1) == Counter(str2)

How do you find the first non-repeating character in a string?

def first_non_repeating_character(s):
  frequency = {}
  for char in s:
    frequency[char] = frequency.get(char, 0) + 1
  for char in s:
    if frequency[char] == 1:
      return char
  return None

How do you convert a Roman numeral to an integer?

def roman_to_int(s):
  roman_numerals = {'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000}
  integer = 0
  for i in range(len(s)):
    if i > 0 and roman_numerals[s[i]] > roman_numerals[s[i - 1]]:
      integer += roman_numerals[s[i]] - 2 * roman_numerals[s[i - 1]]
    else:
      integer += roman_numerals[s[i]]
  return integer

Implement a function to reverse a linked list.

class ListNode:
    def __init__(self, value=0, next=None):
      self.value = value
      self.next = next
  
  def reverse_linked_list(head):
    previous = None
    current = head
    while current:
      next_node = current.next
      current.next = previous
      previous = current
      current = next_node
    return previous

Write a function to check if a binary tree is balanced.

def is_balanced(root):
    def check(node):
      if not node:
        return 0
      left = check(node.left)
      right = check(node.right)
      if left == -1 or right == -1 or abs(left - right) > 1:
        return -1
      return max(left, right) + 1
    return check(root) != -1

Find the longest substring without repeating characters.

def length_of_longest_substring(s):
    char_map = {}
    longest = 0
    left = 0
    for right, char in enumerate(s):
      if char in char_map and char_map[char] >= left:
        left = char_map[char] + 1
      char_map[char] = right
      longest = max(longest, right - left + 1)
    return longest

Given an array of integers, find two numbers such that they add up to a specific target number.

def two_sum(nums, target):
    num_map = {}
    for i, num in enumerate(nums):
      complement = target - num
      if complement in num_map:
        return [num_map[complement], i]
      num_map[num] = i
    return []

Implement a function to merge two sorted linked lists into one sorted linked list.

class ListNode:
    def __init__(self, value=0, next=None):
      self.value = value
      self.next = next
  
  def merge_two_lists(l1, l2):
    dummy = ListNode()
    current = dummy
    while l1 and l2:
      if l1.value < l2.value:
        current.next = l1
        l1 = l1.next
      else:
        current.next = l2
        l2 = l2.next
      current = current.next
    current.next = l1 or l2
    return dummy.next

Design a URL shortening service like bit.ly.

• A RESTful API for shortening URLs and redirecting to the original URL.
• A hashing function to generate a unique short code for each URL.
• A database to store the mapping between the original URL and the short code.
• Handling of high traffic and scalability concerns.

Design a scalable chat service like WhatsApp.

• Real-time messaging and presence indicators.
• Efficient data storage for message history.
• End-to-end encryption for security.
• Push notifications for new messages or events.
• Load balancing and distributed systems to handle concurrent users.

Design a recommendation system like Netflix.

• Collaborative filtering for personalized recommendations.
• Content-based filtering based on user preferences and viewing history.
• Scalable data processing pipelines for real-time recommendations.
• A/B testing framework for experimenting with recommendation algorithms.
• Caching strategies to improve performance and reduce latency.

Design a distributed file storage system like Dropbox.

• File synchronization across devices.
• Chunking files and deduplication for storage efficiency.
• Data consistency and conflict resolution.
• Security measures for data encryption and access control.
• Replication and fault tolerance to ensure data availability.

Design a global ride-sharing service like Uber.

• Geospatial indexing for efficient matching of riders and drivers.
• Dynamic pricing based on demand and supply.
• Payment processing and financial transactions.
• Driver and rider rating systems for quality assurance.
• Real-time notifications and updates for trip status.

Describe a time when you had to deal with a difficult team member.

Tip: Focus on how you approached the situation with empathy, communicated effectively, and worked towards a resolution that benefited the team.

Tell me about a time when you had to adapt to a significant change at work.

Tip: Highlight your flexibility, ability to learn quickly, and how you maintained a positive attitude during the transition.

Give an example of a goal you reached and tell me how you achieved it.

Tip: Discuss the specific actions you took, the obstacles you overcame, and the outcome. Emphasize your determination and strategic planning.

Describe a situation where you had to solve a difficult problem.

Tip: Explain the problem-solving steps you took, including how you identified the problem, the alternatives you considered, and the solution you implemented.

Tell me about a time when you showed leadership.

Tip: Provide an example where you took the lead in a team setting, outlining the leadership qualities you displayed and the results of your actions.