# # leetcode

### LeetCode Notes: Add Digits

LeetCode problem solving notes. Given an integer num, repeatedly add all its digits until the result has only one digit, and return it.

### LeetCode Notes: Binary Tree Paths

LeetCode problem solving notes. Given the root of a binary tree, return all root-to-leaf paths in any order.

### LeetCode Notes: Binary Tree Postorder Traversal

LeetCode problem solving notes. Given the root of aÂ binary tree, return the postorder traversal of its nodes' values.

### LeetCode Notes: Can Place Flowers

LeetCode problem solving notes. You have a long flowerbed in which some of the plots are planted, and some are not. However, flowers cannot be planted in adjacent plots.

### LeetCode Notes: Combine Two Tables

LeetCode problem solving notes. Write a SQL query for a report that provides the following information for each person in the Person table, regardless if there is an address for each of those people.

### LeetCode Notes: Contains Duplicate II

LeetCode problem solving notes. Given an integer array nums and an integer k, return true if there are two distinct indices i and j in the array such that nums[i] == nums[j] and abs(i - j) <= k.

### LeetCode Notes: Counting Bits

LeetCode problem solving notes. Given a non-emptyÂ array of integers nums, every element appears twice except for one. Find that single one.

### LeetCode Notes: Delete the Node of the Linked List

LeetCode problem solving notes. Given the head pointer of the singly linked list and the value of a node to be deleted, define a function to delete the node.

### LeetCode Notes: Excel Sheet Column Number

LeetCode problem solving notes. Given a string columnTitle that represents the column title as appear in an Excel sheet, return its corresponding column number.

### LeetCode Notes: Excel Sheet Column Title

LeetCode problem solving notes. Given an integer columnNumber, return its corresponding column title as it appears in an Excel sheet.