You are given an array of k arrays/linked-lists arrays, each array/linked-list is sorted in ascending or descending order. Merge all the arrays/linked-lists into one sorted array/linked-list and return it. Example 1: Input: arrays= [[1,4,5],[1,3,4],[2,6]] Output: [1,1,2,3,4,4,5,6] Explanation: The arrays/linked-lists are: [ 1->4->5, 1->3->4, 2->6 ] merging them into one sorted array/list: 1->1->2->3->4->4->5->6 Constraints: k == arrays.length 0 <= […]

## Permutation and Combination

Permutation – position (order) matters. = N! / (N – r)!. Building words with {a,b,c} are also permutation problem with r = {1,2,3..N} Combination – position (order) doesn’t matter = N! / (N – r)! * r! . Combination is a part of Permutation set. All possible combination means, generating combination for r = {0,1.. […]

## System Design links

https://github.com/donnemartin/system-design-primer https://github.com/binhnguyennus/awesome-scalability https://www.naniz.co/posts/2020/12/system-design-algorithm-and-interview-cheat-sheet https://www.bennadel.com/blog/3467-the-not-so-dark-art-of-designing-database-indexes-reflections-from-an-average-software-engineer.htm https://www.microsoft.com/en-us/research/wp-content/uploads/2017/09/Kafka.pdf https://www.youtube.com/watch?v=YPbGW3Fnmbc https://docs.microsoft.com/en-us/azure/architecture/reference-architectures/saga/saga https://docs.google.com/document/d/1HkagusVJhCWrdu0lIF0O8foEqybrAnT38cGZIio_oME/edit?usp=sharing

## Important and Useful links from all over the Leetcode

List of all good posts on Leetcode. Comment down whichever I am missing and I will add all of them here – DP for beginners by @wh0ami – https://leetcode.com/discuss/general-discussion/662866/dp-for-beginners-problems-patterns-sample-solutions[LIST – https://leetcode.com/list/x1k8lxi5] Graph for beginners by @wh0ami – https://leetcode.com/discuss/general-discussion/655708/graph-for-beginners-problems-pattern-sample-solutions/562734[LIST – https://leetcode.com/list/x1wy4de7] Sliding window for beginners by @wh0ami – https://leetcode.com/discuss/general-discussion/657507/sliding-window-for-beginners-problems-template-sample-solutions/562721[LIST – https://leetcode.com/list/x1lbzfk3] DP Patterns by @aatalyk – https://leetcode.com/discuss/general-discussion/458695/dynamic-programming-patterns Leetcode patterns from edu_cative_dot_io by @late_riser […]

## Leetcode – 78. Subsets

Given a set of distinct integers, nums, return all possible subsets (the power set). Note: The solution set must not contain duplicate subsets. Solution: Cascading Approach: Lets say, we have a set S={1,2,3,4}. Pick an element from set, ex. 4, now you have 2 sets – {[], [4]}. Now pick the second element from list ex. 3, now you […]

## .NET Big O Algorithm Complexity Cheat-Sheet

## Leetcode 99 – Recover Binary Search Tree – Constant space

Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure with constant space. Example 1: Input: [1,3,null,null,2] 1 / 3 \ 2 Output: [3,1,null,null,2] 3 / 1 \ 2 Example 2: Input: [3,1,4,null,null,2] 3 / \ 1 4 […]

## USACO 2017 January Contest. Problem 1. Cow Dance Show

After several months of rehearsal, the cows are just about ready to put on their annual dance performance; this year they are performing the famous bovine ballet “Cowpelia”. The only aspect of the show that remains to be determined is the size of the stage. A stage of size K can support K cows dancing simultaneously. The N cows in the […]

## 1477. Find Two Non-overlapping Sub-arrays Each With Target Sum

Given an array of integers arr and an integer target. You have to find two non-overlapping sub-arrays of arr each with sum equal target. There can be multiple answers so you have to find an answer where the sum of the lengths of the two sub-arrays is minimum. Return the minimum sum of the lengths of the two required sub-arrays, or return -1 if you cannot find such two […]

## Cut Ribbon

Given an array of integers with elements representing lengths of ribbons. Your goal is to obtain k ribbons of equal length cutting the ribbons into as many pieces as you want. Find the maximum integer length L to obtain at least k ribbons of length L. Example 1: First, we will find the largest length of ribbon, as we […]

## How to Ace Amazon Behavioral Interview

## Computer Networks

Computer Networks. Part One: LANs and WANs Computer Networks. Part Two: Network Hardware Computer Networks. Part Three: Ethernet Fundamentals Computer Networks. Part Four: LAN Topology Computer Networks. Part Five: Switched Ethernet LANs Computer Networks. Part Six: The TCP/IP Protocol Stack and Routers Domain Name System DNS

## Twos complement: Negative numbers in binary

Two’s Complement Representation of Negative Numbers