Recently I receive a request to update the sitemap of a website periodically so that the crawler can get the latest content. A sitemap typically is located at the root of the domain (i.e. yourdomain.com/sitemap.xml). In another word, the sitemap.xml is stored in the public folder of the NextJS project. …

Problem Statement Given the head of a Singly LinkedList that contains a cycle, write a function to find the starting node of the cycle. Key Ideas Point 3 pointers to the head of the linked list — Slow pointer, fast pointer, and entry pointer. Move slow pointer 1 node at a time while moving…

Problem Statement Given an integer array nums, you need to find one continuous subarray that if you only sort this subarray in ascending order, then the whole array will be sorted in ascending order. Return the shortest such subarray and output its length. Key Ideas Consider the case nums = [1, 5, 2, -1…

Problem Statement Given an array with positive numbers and a positive target number, find all of its contiguous subarrays whose product is less than the target number. Key Ideas Keep moving a pointer(right) from the left to the right while keeping a pointer(left) at the left. (sliding window — we expand the window by…

Problem Statement Given an integer array nums of length n and an integer target, find three integers in nums such that the sum is closest to target. Return the sum of the three integers. Key Ideas Use 3 pointers to point to the current element, next(left) element, and the last(right) element. Sum the 3…

Problem Statement Given a string s and a list of words words of the same length. Return all starting indices of substring(s) that is a concatenation of each word exactly once, in any order, and without any intervening characters. Example 1 Input: String="catdogcat", Words=["cat", "dog"] Output: [0, 3] Explanation: The two substring containing both the…

A power set is a set of all subsets of a set, including empty set and the set itself. Let’s look at a few examples to understand what that statement really means. We are at the grocery store, we want to buy apple or banana: {apple, banana} Empty -> {} …

This is just one of the cool things that you can do with XOR. Problem Statement Given an array, find number that occurs odd number of times. Input: [1,2,2,3,3,1,5,1,5,5,5] Output: 1 Understanding XOR (eXclusive OR) The logic is simple. If the bits are the same, the result is 0. If the bits are different, the result…

In short, Brian Kernighan’s Algorithm is used to count the number of 1 (also known as set bits) in a binary number. The main concept here is when we subtract one from any number, all the bits after the least significant/rightmost set bits will be inverted! Let’s look at a…