排序map、pq、stack。固定 递归 贪心 开关 二分 滑动窗口（固递贪开二滑）

摘要： You are given a perfect binary tree where all leaves are on the same level, and every parent has two children. The binary tree has the following defin 阅读全文

摘要： 思路：就是把gcd拆一下，因为如果GCD可以，这些数就也可以3，6 gcd = n = 3 1/3 没了，0 += 2 GCD辗转相除法：b一开始是除数，后来是余数。余数为0就行了 16 4 4，4 4，0 所以返回a = 4 https://www.geeksforgeeks.org/common 阅读全文

摘要： Given a nested list of integers, implement an iterator to flatten it. Each element is either an integer, or a list -- whose elements may also be integ 阅读全文

摘要： Given an array nums with n objects colored red, white, or blue, sort them in-place so that objects of the same color are adjacent, with the colors in 阅读全文

摘要： Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: 阅读全文

摘要： Given a collection of distinct integers, return all possible permutations. Example: Input: [1,2,3] Output: [ [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1, 阅读全文

摘要： Given a list of words and two words word1 and word2, return the shortest distance between these two words in the list. Example:Assume that words = ["p 阅读全文

摘要： Given a column title as appear in an Excel sheet, return its corresponding column number. For example: A -> 1 B -> 2 C -> 3 ... Z -> 26 AA -> 27 AB -> 阅读全文

摘要： Given a list of non-negative integers nums, arrange them such that they form the largest number. Note: The result may be very large, so you need to re 阅读全文

摘要： Given an array of strings strs, group the anagrams together. You can return the answer in any order. An Anagram is a word or phrase formed by rearrang 阅读全文