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MOST COMMON Dropbox CODING INTERVIEW QUESTIONS
The 15 most asked questions in dropbox interview
ARRAYS
Determine if the sum of three integers is equal to the given value
Problem statement
Given an array of integers and a value, determine if there are any three integers in the array whose sum equals the given value.
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Merge overlapping intervals
Problem statement
Given a list of intervals, merge all the overlapping intervals to produce a list that has only mutually exclusive intervals.
LINKED LISTS
Add two integers
Problem statement
Given the head pointers of two linked lists where each linked list represents an integer number (each node is a digit), add them and return the resulting linked list.
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Merge two sorted linked lists
Problem statement
Given two sorted linked lists, merge them so that the resulting linked list is also sorted.
TREES
Determine if two binary trees are identical
Problem statement
Given the roots of two binary trees, determine if these trees are identical or not. Identical trees have the same layout and data at each node.
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Mirror binary tree nodes
Problem statement
Given the root node of a binary tree, swap the ‘left’ and ‘right’ children for each node.
STRINGS
Find all palindrome substrings
Problem statement
Given a string find all non-single letter substrings that are palindromes.
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Reverse words in a sentence
Problem statement
Reverse the order of words in a given sentence (an array of characters).
DYNAMIC PROGRAMMING
Find the maximum sum of a subarray
Problem statement
Given an array of positive numbers and a positive number ‘k’, find the maximum sum of any contiguous subarray of size ‘k’.
MATH AND STATS
Power of a number
Problem statement
Given a double, ‘x’, and an integer, ‘n’, write a function to calculate ‘x’ raised to the power ‘n’.
BACKTRACKING
Find all sum combinations
Problem statement
Given a positive integer, target, print all possible combinations of positive integers that sum up to the target number.
GRAPHS
Clone a directed graph
Problem statement
Given the root node of a directed graph, clone this graph by creating its deep copy so that the cloned graph has the same vertices and edges as the original graph.
DESIGN
Implement a LRU cache
Problem statement
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
Search in rotated array
Problem statement
Search for a given number in a sorted array that has been rotated by some arbitrary number. Return -1 if the number does not exist. Assume that the array does not contain duplicates.
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Merge overlapping intervals
Problem statement
Given a list of intervals, merge all the overlapping intervals to produce a list that has only mutually exclusive intervals.