Source: https://leetcode.com/problems/design-twitter/
Design a simplified version of Twitter where users can post tweets, follow/unfollow another user and is able to see the 10 most recent tweets in the user’s news feed. Your design should support the following methods:
Source: https://leetcode.com/problems/intersection-of-two-arrays-ii/
Given two arrays, write a function to compute their intersection.
Source: https://leetcode.com/problems/intersection-of-two-arrays/
Given two arrays, write a function to compute their intersection.
Source: https://leetcode.com/problems/top-k-frequent-elements/
Given a non-empty array of integers, return the k most frequent elements.
Source: https://leetcode.com/problems/bulls-and-cows/
You are playing the following Bulls and Cows game with your friend: You write down a number and ask your friend to guess what the number is. Each time your friend makes a guess, you provide a hint that indicates how many digits in said guess match your secret number exactly in both digit and position (called “bulls”) and how many digits match the secret number but locate in the wrong position (called “cows”). Your friend will use successive guesses and hints to eventually derive the secret number.
Source：https://leetcode.com/problems/word-pattern/
Given a pattern and a string str, find if str follows the same pattern.
Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty word in str.
Source: https://leetcode.com/problems/contains-duplicate-ii/
Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j]and the absolute difference between i and j is at most k.
Given two strings s and t, determine if they are isomorphic.
Source：https://leetcode.com/problems/happy-number/
Write an algorithm to determine if a number is “happy”.