Cloudflare Interview Questions and Answers

Swap kth and kth to last element of a singly linked list in one pass without knowing the length of the list.

• Traverse the linked list using two pointers, one starting from the head and the other starting from kth node.

• When the second pointer reaches the end of the list, the first pointer will be pointing to the kth to last node.

• Swap the values of kth and kth to last node.

• Handle edge cases such as k being out of bounds o...read more

Program to reverse the ordering of words in a sentence

• Split the sentence into an array of words

• Reverse the array

• Join the array into a sentence

Program to find intersection point of two singly linked lists in O(n)

• Traverse both lists and find their lengths

• Move the head of the longer list by the difference in lengths

• Traverse both lists in parallel until intersection point is found

• Return the intersection point

Program to reverse a singly linked list both recursively and iteratively

• Iteratively: Use three pointers to reverse the links between nodes

• Recursively: Use a recursive function to reverse the links between nodes

• In both approaches, update the head and tail pointers accordingly

Find odd weight ball among 12 identical balls using a balance in minimum weighings.

• Divide balls into 3 groups of 4 each

• Weigh any 2 groups against each other

• If both groups weigh the same, the odd ball is in the third group

• If one group is heavier, weigh any 2 balls from that group against each other

• If they weigh the same, the odd ball is the remaining one

• If one ball is heavier, it is the odd ball

• Repeat the process with t

A program to reverse a singly linked list in groups of k using recursion.

• Create a recursive function that takes the head of the linked list and the group size as parameters.

• If the remaining list has less than k nodes, return the head as it is.

• Reverse the first k nodes by recursively calling the function for the next group.

• Connect the reversed group to the remaining list.

• Return the new head of the reversed list.

Program to find length of longest substring without repeating characters in a string.

• Use a sliding window approach to traverse the string

• Use a hash set to keep track of unique characters in the current substring

• Update the length of longest substring without repeating characters as you traverse the string

Representing date of a month using two cubes with numbers 0-9 on each face

• Assign numbers 0-9 on each face of both cubes

• Use one cube to represent tens digit and other for ones digit

• Rotate cubes to display desired date

• Example: Cube 1 - 0, 1, 2, 3, 4, 5; Cube 2 - 0, 1, 2, 6, 7, 8; To represent 23, Cube 1 shows 2 and Cube 2 shows 3

Find the character repeated most number of times in an array of strings.

• Create a dictionary to store character count

• Iterate through each string and character

• Return the character with highest count

Answering a question on tracing output of C/C++ code snippet with pointers and references

• Understand the code and identify all pointers and references

• Trace the values of each pointer and reference at each step

• Follow the flow of the code to determine the final output

Segmentation fault is a type of error that occurs when a program tries to access a memory location that it is not allowed to access.

• Segmentation fault is also known as a segfault.

• It is a common error in C and C++ programming languages.

• It occurs when a program tries to read or write to a memory location that it does not have permission to access.

• This can happen when a program tries to access an uninitialized pointer or ...read more

BFS and DFS are graph traversal algorithms used to search for nodes in a graph.

• BFS stands for Breadth First Search and explores all the nodes at the current depth before moving to the next level.

• DFS stands for Depth First Search and explores as far as possible along each branch before backtracking.

• BFS uses a queue data structure while DFS uses a stack or recursion.

• BFS is useful for finding the shortest path in an unwei...read more

I would prefer Depth First Search (DFS) traversal for finding a cycle in a graph.

• DFS is better suited for finding cycles in a graph as it explores deeper into the graph before backtracking.

• DFS can detect a cycle in a graph in O(V+E) time complexity.

• DFS can be implemented using recursion or a stack.

• Breadth First Search (BFS) can also be used to find cycles but it is less efficient than DFS.

• In DFS, we can keep track of v

Hashmap has constant time complexity for insertion, deletion, and retrieval, but requires additional space.

• Hashmap provides constant time complexity O(1) for insertion, deletion, and retrieval operations on average.

• The space complexity of a hashmap is proportional to the number of elements stored in it.

• Hashmap uses a hash function to map keys to indices in an underlying array, which allows for efficient lookup.

• In case ...read more

The data structure behind a login page should store user credentials securely.

• Use a database to store user information

• Hash and salt passwords for security

• Include fields for username, email, password, and possibly additional information

• Consider implementing two-factor authentication