Joy Coder

算法题目：Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this binary tree is symmetric: But the following is not: Note: Bonus points if you c

算法题目：Given two binary strings, return their sum (also a binary string).For example, a = “11” b = “1” Return “100”大致意思：二进制字符串的加法解题思路：可以用循环与递归来求解循环版本： string addBinary(string a, string b) {

算法题目：The API: int read4(char *buf) reads 4 characters at a time from a file. The return value is the actual number of characters read. For example, it returns 3 if there is only 3 characters left in t

算法题目：Design and implement a TwoSum class. It should support the following operations: add and find.add - Add the number to an internal data structure. find - Find if there exists any pair of numbers w

算法题目：Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.Note: You may assume that nums1 has enough space (size that is greater or equal to m + n) to hold addit

算法题目：Given a binary tree, determine if it is height-balanced.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 diffe

算法题目：Given a string containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[’ and ‘]’, determine if the input string is valid. The brackets must close in the correct order, “()” 、 “()[]{}” and “([])[{()

算法题目：Given n non-negative integers a1, a2, …, an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find tw

算法题目：Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.For example: Given the below binary tree and su

hashmap实现