Let’s solve a medium problem together on Leetcode.com: Count and Say

The count-and-say sequence is a sequence of digit strings defined by the recursive formula:

countAndSay(1) = "1"

countAndSay(n) is the way you would "say" the digit string from countAndSay(n-1), which is then converted into a different digit string.


Sorting algorithms are frequently asked during a technical interview. Several common sorting algorithms such as quicksort, selection sort, merge sort are usually applied to sorting a list. However, sorting a linked list is not straightforward: it’s not easy to access an element by index in constant running time. Most of…


A singly linked list is a set of linked nodes. Different from a singly linked list, each node in a doubly linked list has an extra pointer points to its previous node. Today, I’ll talk about the implementation of a doubly linked list in python.

A doubly linked…

The sliding window algorithm is often used to find the target number in a string/list. Today, I’ll introduce how to solve this leetcode problem using the sliding window algorithm and optimize its running time.

You are given an array of integers nums, there is a sliding window of size k

My previous post introduced the Knapsack problem. It states how to solve using the dynamic programming algorithm. Besides Knapsack, there’s one series of problems that you might encounter in a coding interview: the house robber problems. Today, let’s talk about it.

You are a professional robber planning to rob houses…


on the way to become a programmer

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