| class Solution { | |
| int[] cache; | |
| public int reversePairs(int[] nums) { | |
| int n = nums.length; | |
| cache = new int[n]; | |
| return count(nums, 0, n-1); | |
| } | |
| int count(int[] arr, int l, int r){ | |
| if(l==r) return 0; |
I liked the way Grokking the coding interview organized problems into learnable patterns. However, the course is expensive and the majority of the time the problems are copy-pasted from leetcode. As the explanations on leetcode are usually just as good, the course really boils down to being a glorified curated list of leetcode problems.
So below I made a list of leetcode problems that are as close to grokking problems as possible.
| class QueueStack { | |
| constructor() { | |
| this.q = []; | |
| } | |
| push(val) { | |
| let size = this.q.length; | |
| this.q.push(val); | |
| while (size--) { | |
| this.q.push(this.q.shift()); | |
| } |
| class Solution { | |
| public List<List<Integer>> levelOrder(TreeNode root) { | |
| List<List<Integer>> ans=new ArrayList<>(); | |
| if(root==null) return ans; | |
| List<Integer> level=new ArrayList<>(); | |
| Queue<TreeNode> q=new LinkedList<>(); | |
| q.offer(root); | |
| q.offer(null); |
| // Given an unsorted integer array nums, find the smallest missing positive integer. | |
| // You must implement an algorithm that runs in O(n) time and uses constant extra space. | |
| // https://leetcode.com/problems/first-missing-positive/ | |
| var firstMissingPositive = function (nums) { | |
| for (let i = 0; i < nums.length; i++) { | |
| if (nums[i] > 0 && nums[i] <= nums.length && nums[i] !== i + 1) { | |
| [nums[i], nums[nums[i] - 1]] = [nums[nums[i] - 1], nums[i]]; | |
| i = i - 1; |
