most common twitter coding interview questions
the 15 most asked questions in a twitter interview
Arrays
Determine if the sum of two integers is equal to the given value
Problem statement
Given an array of integers and a value, determine if there are any two integers in the array whose sum is equal to the given value.
Set columns and rows as zeros
Problem statement
Given a two-dimensional array, if any element within is zero, make its whole row and column zero.
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.
Copy linked list with arbitrary pointer
Problem statement
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.
trees
Level order traversal of binary tree
Problem statement
Given the root of a binary tree, display the node values at each level.
Connect all siblings
Problem statement
Connect the sibling pointer to the next node in the same level. The last node in each level should point to the first node of the next level in the tree.
strings
Reverse words in a sentence
Problem statement
Reverse the order of words in a given sentence(an array of characters).
Find all palindrome substrings
Problem statement
Given a string find all non-single letter substrings that are palindromes.
dynamic programming
Find maximum single sell profit
Problem statement
Given a list of daily stock prices (integers for simplicity), return the buy and sell prices for making the maximum profit. You need to maximize the single buy/sell profit. If you can't make any profit, try to minimize the loss.
Math and stats
Find the missing number in the array
Problem statement
You are given an array of positive numbers from 1 to n, such that all numbers from 1 to n are present except one number 'x'. We have to find 'x'. The input array is not sorted.
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.
backtracking
Regular expression matching
Problem statement
Given a text and a pattern, determine if the pattern matches with the text completely or not at all by using regular expression matching. For simplicity, assume that the pattern may contain only two operators: '.' and '*'. Operator '*' in the pattern means that the character preceding '*' may not appear or may appear any number of times in the text. Operator '.' matches with any character in the text exactly once.
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.
sorting and searching
Closest meeting point
Problem statement
Given N people on an MxM grid, find the point that requires the least total distance covered by all people to meet at that point.
Search for the given key in a 2d matrix
Problem statement
We are given a 2D array where all elements in any individual row or column are sorted. In such a matrix, we have to search or find the position of a given key.
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