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

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 >>