You can preview the content of the codes and can downlode a zip file of the codes in the view buton above
The data structure and algorithms are the core of computer programing languages will come and go but data structure algoeithms are going to be there for long.
- day 1 This problem was recently asked by Google.
Given a list of numbers and a number k, return whether any two numbers from the list add up to k.
For example, given [10, 15, 3, 7] and k of 17, return true since 10 + 7 is 17.
- day 3 The Sieve of Eratosthenes is an algorithm used to generate all prime numbers smaller than N. The method is to take increasingly larger prime numbers, and mark their multiples as composite.
For example, to find all primes less than 100, we would first mark [4, 6, 8, ...] (multiples of two), then [6, 9, 12, ...] (multiples of three), and so on. Once we have done this for all primes less than N, the unmarked numbers that remain will be prime.
- day 4 This problem was asked by Spotify.
There are N couples sitting in a row of length 2 * N. They are currently ordered randomly, but would like to rearrange themselves so that each couple's partners can sit side by side.
What is the minimum number of swaps necessary for this to happen?
- day 7 This problem was asked by Facebook.
Suppose you are given two lists of n points, one list p1, p2, ..., pn on the line y = 0 and the other list q1, q2, ..., qn on the line y = 1. Imagine a set of n line segments connecting each point pi to qi. Write an algorithm to determine how many pairs of the line segments intersect.
- day 9 This problem was asked by Google.
Given an array of elements, return the length of the longest subarray where all its elements are distinct.
For example, given the array [5, 1, 3, 5, 2, 3, 4, 1], return 5 as the longest subarray of distinct elements is [5, 2, 3, 4, 1].
- day 10 This problem was asked by Uber.
Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand. Find the minimum element in O(log N) time. You may assume the array does not contain duplicates.
For example, given [5, 7, 10, 3, 4], return 3.
-
day 11 This problem was asked by Google. Given the head of a singly linked list, swap every two nodes and return its head. For example, given 1 -> 2 -> 3 -> 4, return 2 -> 1 -> 4 -> 3
-
day 12 This problem was asked by Bloomberg.
Determine whether there exists a one-to-one character mapping from one string s1 to another s2.
For example, given s1 = abc and s2 = bcd, return true since we can map a to b, b to c, and c to d.
Given s1 = foo and s2 = bar, return false since the o cannot map to two characters.
-
day 13 Given a circular array, compute its maximum subarray sum in O(n) time. A subarray can be empty, and in this case the sum is 0. For example, given [8, -1, 3, 4], return 15 as we choose the numbers 3, 4, and 8 where the 8 is obtained from wrapping around. Given [-4, 5, 1, 0], return 6 as we choose the numbers 5 and 1.
-
day 17 Given n numbers, find the greatest common denominator between them. For example, given the numbers [42, 56, 14], return 14.
-
day 18 Given a list of elements, find the majority element, which appears more than half the time (> floor(len(lst) / 2.0)). You can assume that such element exists. For example, given [1, 2, 1, 1, 3, 4, 0], return 1.
-
day 21 Given an unsigned 8-bit integer, swap its even and odd bits. The 1st and 2nd bit should be swapped, the 3rd and 4th bit should be swapped, and so on.
For example, 10101010 should be 01010101. 11100010 should be 11010001.
Bonus: Can you do this in one line?
- day 23 Given a string, determine whether any permutation of it is a palindrome.
For example, carrace should return true, since it can be rearranged to form racecar, which is a palindrome. daily should return false, since there's no rearrangement that can form a palindrome.
- day 24 Given a set of closed intervals, find the smallest set of numbers that covers all the intervals. If there are multiple smallest sets, return any of them.
For example, given the intervals [0, 3], [2, 6], [3, 4], [6, 9], one set of numbers that covers all these intervals is {3, 6}.
-
day 26 You are given an array of length n + 1 whose elements belong to the set {1, 2, ..., n}. By the pigeonhole principle, there must be a duplicate. Find it in linear time and space.
-
day 27 Given a 32-bit integer, return the number with its bits reversed.
For example, given the binary number 1111 0000 1111 0000 1111 0000 1111 0000, return 0000 1111 0000 1111 0000 1111 0000 1111.
-
day28 Given a real number n, find the square root of n. For example, given n = 9, return 3.
-
day29 Gray code is a binary code where each successive value differs in only one bit, as well as when wrapping around. Gray code is common in hardware so that we don't see temporary spurious values during transitions.
Given a number of bits n, generate a possible gray code for it.
The edit distance between two strings refers to the minimum number of character insertions, deletions, and substitutions required to change one string to the other. For example, the edit distance between “kitten” and “sitting” is three: substitute the “k” for “s”, substitute the “e” for “i”, and append a “g”.
Given two strings, compute the edit distance between them.
-
38 Given a number in the form of a list of digits, return all possible permutations.
-
day40 This problem was asked by Facebook.
Given an array of integers in which two elements appear exactly once and all other elements appear exactly twice, find the two elements that appear only once.
- day42 You are given an array of nonnegative integers. Let's say you start at the beginning of the array and are trying to advance to the end. You can advance at most, the number of steps that you're currently on. Determine whether you can get to the end of the array.
For example, given the array [1, 3, 1, 2, 0, 1], we can go from indices 0 -> 1 -> 3 -> 5, so return true.
Given the array [1, 2, 1, 0, 0], we can't reach the end, so return false.
- day43 You have n fair coins and you flip them all at the same time. Any that come up tails you set aside. The ones that come up heads you flip again. How many rounds do you expect to play before only one coin remains?
Write a function that, given n, returns the number of rounds you'd expect to play until one coin remains.
- day51 Given a function f, and N return a debounced f of N milliseconds.
That is, as long as the debounced f continues to be invoked, f itself will not be called for N milliseconds.
- day52 This problem was asked by Microsoft.
A number is considered perfect if its digits sum up to exactly 10.
Given a positive integer n, return the n-th perfect number.
For example, given 1, you should return 19. Given 2, you should return 28.
- day53 This problem was asked by Amazon.
Given a N by M matrix of numbers, print out the matrix in a clockwise spiral.
For example, given the following matrix:
[[1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, 13, 14, 15], [16, 17, 18, 19, 20]]
You should print out the following:
1 2 3 4 5 10 15 20 19 18 17 16 11 6 7 8 9 14 13 12
- day54 This problem was asked by LinkedIn.
Given a linked list of numbers and a pivot k, partition the linked list so that all nodes less than k come before nodes greater than or equal to k.
For example, given the linked list 5 -> 1 -> 8 -> 0 -> 3 and k = 3, the solution could be 1 -> 0 -> 5 -> 8 -> 3.
This problem was asked by Google.
Given a sorted list of integers, square the elements and give the output in sorted order.
For example, given [-9, -2, 0, 2, 3], return [0, 4, 4, 9, 81].
Given a list of possibly overlapping intervals, return a new list of intervals where all overlapping intervals have been merged.
The input list is not necessarily ordered in any way.
For example, given [(1, 3), (5, 8), (4, 10), (20, 25)], you should return [(1, 3), (4, 10), (20, 25)].
Given a array of numbers representing the stock prices of a company in chronological order, write a function that calculates the maximum profit you could have made from buying and selling that stock once. You must buy before you can sell it.
For example, given [9, 11, 8, 5, 7, 10], you should return 5, since you could buy the stock at 5 dollars and sell it at 10 dollars.
This problem was asked by Google.
Given k sorted singly linked lists, write a function to merge all the lists into one sorted singly linked list.
iven a string of digits, generate all possible valid IP address combinations.
IP addresses must follow the format A.B.C.D, where A, B, C, and D are numbers between 0 and 255. Zero-prefixed numbers, such as 01 and 065, are not allowed, except for 0 itself.
For example, given "2542540123", you should return ['254.25.40.123', '254.254.0.123'].
Given a string of round, curly, and square open and closing brackets, return whether the brackets are balanced (well-formed).
For example, given the string "([])", you should return true.
Given the string "([)]" or "((()", you should return false.
Given an array of numbers, find the length of the longest increasing subsequence in the array. The subsequence does not necessarily have to be contiguous.
For example, given the array [0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15], the longest increasing subsequence has length 6: it is 0, 2, 6, 9, 11, 15.
Run-length encoding is a fast and simple method of encoding strings. The basic idea is to represent repeated successive characters as a single count and character. For example, the string "AAAABBBCCDAA" would be encoded as "4A3B2C1D2A".
Implement run-length encoding and decoding. You can assume the string to be encoded have no digits and consists solely of alphabetic characters. You can assume the string to be decoded is valid
Given three 32-bit integers x, y, and b, return x if b is 1 and y if b is 0, using only mathematical or bit operations. You can assume b can only be 1 or 0.
Given two singly linked lists that intersect at some point, find the intersecting node. The lists are non-cyclical.
For example, given A = 3 -> 7 -> 8 -> 10 and B = 99 -> 1 -> 8 -> 10, return the node with value 8.
In this example, assume nodes with the same value are the exact same node objects.
Do this in O(M + N) time (where M and N are the lengths of the lists) and constant space.
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent