At a lemonade stand, each lemonade costs $5. Customers are standing in a queue to buy from you, and order one at a time (in the order specified by bills). Each customer will only buy one lemonade and pay with either a $5, $10, or $20 bill.  You must…

Given a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus sum of all keys greater than the original key in BST. Example: Input: The root of a Binary Search Tree like thi…

problem 860. Lemonade Change solution class Solution { public: bool lemonadeChange(vector<int>& bills) { , ten = ; for(auto bill:bills) { ) five++; ) { ten++; five--; } ) { ten--; five--; } ; ) return false; } return true; } }; 参考 1. Leetcode_ea…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 日期 题目地址:https://leetcode.com/problems/lemonade-change/description/ 题目描述 At a lemonade stand, each lemonade costs $5. Customers are standing in a queue to buy from you, and orde…

International Morse Code defines a standard encoding where each letter is mapped to a series of dots and dashes, as follows: "a"maps to ".-", "b" maps to "-...", "c" maps to "-.-.", and so on. Fo…

Given an array where elements are sorted in ascending order, convert it to a height balanced BST. For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more th…

Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1. Examples: s = "leetcode" return 0. s = "loveleetcode", return 2. Note: You may assume the string contain only lowercase…

We want to use quad trees to store an N x N boolean grid. Each cell in the grid can only be true or false. The root node represents the whole grid. For each node, it will be subdivided into four children nodes until the values in the region it repres…

Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -. Example 1: Input: a = 1, b = 2 Output: 3 Example 2: Input: a = -2, b = 3 Output: 1   class Solution(object): def getSum(self, a, b): """ :type a…

Given a word, you need to judge whether the usage of capitals in it is right or not. We define the usage of capitals in a word to be right when one of the following cases holds: All letters in this word are capitals, like "USA". All letters in t…