题目 Given a non-empty binary tree, return the average value of the nodes on each level in the form of an array.…

题目 Given an integer, return its base 7 string representation. Example 1: Input: 100 Output: “202” …

题目描述 Given a positive integer, output its complement number. The complement strategy is to flip the bits of it…

题目 Given an array of integers, every element appears twice except for one. Find that single one. Note: Your al…

题目 You are given a string representing an attendance record for a student. The record only contains the follow…

题目 Given a Binary Search Tree and a target number, return true if there exist two elements in the BST such tha…

题目 Given scores of N athletes, find their relative ranks and the people with the top three highest scores, who…

题目 Given a non-negative integer num, repeatedly add all its digits until the result has only one digit. For ex…

题目 Given an array of 2n integers, your task is to group these integers into n pairs of integer, say (a1, b1), …

题目 Given an integer, write an algorithm to convert it to hexadecimal. For negative integer, two’s complement m…

题目 Given n points in the plane that are all pairwise distinct, a “boomerang” is a tuple of points …

题目 Write an algorithm to determine if a number is “happy”. A happy number is a number defined by t…