In 91

LeetCode 58: Length of Last Word

Leet Code 題目 121: Best Time to Buy and Sell Stock

LeetCode 136 題：Single Number

LeetCode 第 15 題: 3 Sum。

LeetCode 第三題 "Longest Substring Without Repeating Characters" 

LeetCode 第 231 題："Power of Two"，相當單純的題目。

Given an integer, write a function to determine if it is a power of two.

LeetCode 第九題 Palindrome Number ，判斷一個數字是否為「回文」。

Determine whether an integer is a palindrome. Do this without extra space. 

 LeetCode 的第 1 題 "Two Sum"，題目描述如下。

用 TDD 來練習完成 LeetCode 的第 2 題，題目描述如下。

LeetCode 326: Power of Three

Given an integer, write a function to determine if it is a power of three.

Follow up:
Could you do it without using any loop / recursion?

用 TDD 來練習完成 leet code 的第 220 題，題目描述如下。

Given an array of integers, find out whether there are two distinct indices i and j in the array such that the absolute difference between nums[i] and nums[j] is at most t and the absolute difference between i and j is at most k.

用 TDD 來練習完成 leet code 的第 219 題，題目描述如下。

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.