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.. … Continue reading Permutation and Combination


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%5BLISThttps://leetcode.com/list/x1k8lxi5%5DGraph for beginners by @wh0ami - https://leetcode.com/discuss/general-discussion/655708/graph-for-beginners-problems-pattern-sample-solutions/562734%5BLISThttps://leetcode.com/list/x1wy4de7%5DSliding window for beginners by @wh0ami - https://leetcode.com/discuss/general-discussion/657507/sliding-window-for-beginners-problems-template-sample-solutions/562721%5BLISThttps://leetcode.com/list/x1lbzfk3%5DDP Patterns by @aatalyk - https://leetcode.com/discuss/general-discussion/458695/dynamic-programming-patternsLeetcode patterns from edu_cative_dot_io by @late_riser - https://leetcode.com/discuss/general-discussion/457546/LeetCode-Problem-Patterns-from-***List of questions sorted … Continue reading Important and Useful links from all over the Leetcode


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 … Continue reading Leetcode – 78. Subsets

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 … Continue reading Leetcode 99 – Recover Binary Search Tree – Constant space

How to Ace Amazon Behavioral Interview

99-how-to-ace-amazon-behavioral-interview-leetcode-discussDownload https://www.youtube.com/playlist?list=PLLucmoeZjtMQK8T111wCvqnfOd0qGFqzL https://www.youtube.com/watch?v=B-xdfQv3I1k&list=PLLucmoeZjtMQK8T111wCvqnfOd0qGFqzL https://www.youtube.com/watch?v=xYzcbQ8iRps&list=PLLucmoeZjtMQwITifg_mEGz6W5H6mbDwJ https://www.youtube.com/watch?v=YBCIlDpNUGo&list=PLLucmoeZjtMSl5kTg7IjPkVGy7kUEbqsG

Computer Networks

Computer Networks. Part One: LANs and WANs https://www.youtube.com/watch?v=ApbOARvYZY4 Computer Networks. Part Two: Network Hardware https://www.youtube.com/watch?v=maG8gHMLfl4&t=356s Computer Networks. Part Three: Ethernet Fundamentals https://www.youtube.com/watch?v=tSB9aAKBN5s&t=1s Computer Networks. Part Four: LAN Topology https://www.youtube.com/watch?v=b0zX03N-FIU Computer Networks. Part Five: Switched Ethernet LANs https://www.youtube.com/watch?v=iH-BQ4hHhRY&t=1s Computer Networks. Part Six: The TCP/IP Protocol Stack and Routers https://www.youtube.com/watch?v=ojT2Iza0I00 Domain Name System DNS https://www.youtube.com/watch?v=yDAHSM2Pijc

Binary Left Shift << and Right Shift >>

Binary Left Shift << When shifting left, the most-significant bit is lost, and a 0 bit is inserted on the right end. Left shift is equivalent to multiplying the bit pattern by 2k (if we are shifting k bits). 10 << 2  = 10 * 22 = 10 * 4 = 40 10 << 3 = 10 … Continue reading Binary Left Shift << and Right Shift >>

Leetcode – 117. Populating Next Right Pointers in Each Node II

Given a binary tree struct Node { int val; Node *left; Node *right; Node *next; } Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL. Initially, all next pointers are set to NULL. Example: Input: {"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":null,"right":null,"val":4},"next":null,"right":{"$id":"4","left":null,"next":null,"right":null,"val":5},"val":2},"next":null,"right":{"$id":"5","left":null,"next":null,"right":{"$id":"6","left":null,"next":null,"right":null,"val":7},"val":3},"val":1} Output: {"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":{"$id":"4","left":null,"next":{"$id":"5","left":null,"next":null,"right":null,"val":7},"right":null,"val":5},"right":null,"val":4},"next":{"$id":"6","left":null,"next":null,"right":{"$ref":"5"},"val":3},"right":{"$ref":"4"},"val":2},"next":null,"right":{"$ref":"6"},"val":1} Explanation: Given … Continue reading Leetcode – 117. Populating Next Right Pointers in Each Node II