most common Google coding interview questions
Below is a list of the 15 most frequently asked questions in a Google interview
For detailed solutions to each question, you can visit
Grokking the Coding Interview: Patterns for Coding Questions
find the kth largest element in a number stream
Design a class to efficiently find the Kth largest element in a stream of numbers. The class should have the following two things:
The constructor of the class should accept an integer array containing initial numbers from the stream and an integer ‘K’.
The class should expose a function add(int num) which will store the given number and return the Kth largest number.
find 'k' closest points to the origin
Given an array of points in a 2D plane, find ‘K’ closest points to the origin.
delete node with given key
You are given the head of a linked list and a key. You have to delete the node that contains this given key.
Copy linked list with arbitrary pointer
You are given a linked list where the node has two pointers. The first is the regular ‘next’ pointer. The second pointer is called ‘arbitrary_pointer’ and it can point to any node in the linked list.
Your job is to write code to make a deep copy of the given linked list. Here, deep copy means that any operations on the original list (inserting, modifying and removing) should not affect the copied list.
Mirror binary trees
Given the root node of a binary tree, swap the 'left' and 'right' children for each node.
find all paths for a sum
Given a binary tree and a number ‘S’, find all paths from root-to-leaf such that the sum of all the node values of each path equals ‘S’.
longest substring with no more than 'k' distinct characters
Given a string, find the length of the longest substring in it with no more than K distinct characters.
longest substring with no repeating characters
Given a string, find if its letters can be rearranged in such a way that no two same characters come next to each other.
equal subset sum partition
Given a set of positive numbers, find if we can partition it into two subsets such that the sum of elements in both subsets is equal.
Math and stats
Determine if the number is valid
Given an input string, determine if it makes a valid number or not. For simplicity, assume that white spaces are not present in the input.
print balanced brace combinations
Print all braces combinations for a given value 'N' so that they are balanced.
Given a number of tasks, determine if they can all be scheduled
There are ‘N’ tasks, labeled from ‘0’ to ‘N-1’. Each task can have some prerequisite tasks which need to be completed before it can be scheduled. Given the number of tasks and a list of prerequisite pairs, find out if it is possible to schedule all the tasks.
implement a lru cache
Least Recently Used (LRU) is a common caching strategy. It defines the policy to evict elements from the cache to make room for new elements when the cache is full, meaning it discards the least recently used items first.
sorting and searching
find the high and low index
Given a sorted array of integers, return the low and high index of the given key. Return -1 if not found. The array length can be in the millions with many duplicates.
merge overlapping intervals
You are given an array (list) of interval pairs as input where each interval has a start and end timestamp. The input array is sorted by starting timestamps. You are required to merge overlapping intervals and return output array (list).
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