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 <= […]
Category: Algorithm
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:
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 […]
Leetcode – 968 – Binary Tree Cameras
Given a binary tree, we install cameras on the nodes of the tree. Each camera at a node can monitor its parent, itself, and its immediate children. Calculate the minimum number of cameras needed to monitor all nodes of the tree. Example 1: Input: [0,0,null,0,0] Output: 1 Explanation: One camera is enough to monitor all nodes if placed […]
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 […]
Leetcode 685 – Redundant Connection II
In this problem, a rooted tree is a directed graph such that, there is exactly one node (the root) for which all other nodes are descendants of this node, plus every node has exactly one parent, except for the root node which has no parents. The given input is a directed graph that started as a rooted […]