随笔分类 - Level 2
摘要：Given a string s containing only three types of characters: '(', ')' and '*', return true if s is valid. The following rules define a valid string: An
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摘要：Given the root of 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
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摘要：Some people will make friend requests. The list of their ages is given and ages[i] is the age of the ith person. Person A will NOT friend request pers
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摘要：Given an array of integers nums, calculate the pivot index of this array. The pivot index is the index where the sum of all the numbers strictly to th
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摘要：Given an integer array arr, remove a subarray (can be empty) from arr such that the remaining elements in arr are non-decreasing. A subarray is a cont
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摘要：Given an array consists of non-negative integers, your task is to count the number of triplets chosen from the array that can make triangles if we tak
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摘要：Given the root of a binary tree, find the maximum average value of any subtree of that tree. (A subtree of a tree is any node of that tree plus all it
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摘要：第二题 给两个数组，两个数组中的元素都是pair<int, int>，数组表示压缩后的一串数字 A: [(1, 2), (3,1), (2,3), (3, 1)] 表示 {1, 1, 3, 2, 2, 2, 3} B: [(5, 1), (1,1), (3,4), (2, 1)] 表示 {5, 1,
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摘要：A complete binary tree is a binary tree in which every level, except possibly the last, is completely filled, and all nodes are as far left as possibl
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摘要：第一题一个四位数的密码锁，初始状态为0000， 输入解锁密码，返回最少多少个move可以解开。热身题，考虑几个异常输入即可。 比如说输入 1111， 结果是4输入0000， 结果是0 输入9999， 结果是4 就是算一下每一位input算 Math.Min(input - '0', '9' - in
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摘要：From any string, we can form a subsequence of that string by deleting some number of characters (possibly no deletions). Given two strings source and
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摘要：You are given a sorted array consisting of only integers where every element appears exactly twice, except for one element which appears exactly once.
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摘要：Given a non-empty string s and an abbreviation abbr, return whether the string matches with the given abbreviation. A string such as "word" contains o
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摘要：Given a list of folders, remove all sub-folders in those folders and return in any order the folders after removing. If a folder[i] is located within
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摘要：Given a string s and a list of strings dict, you need to add a closed pair of bold tag <b> and </b> to wrap the substrings in s that exist in dict. If
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摘要：Create a timebased key-value store class TimeMap, that supports two operations. 1. set(string key, string value, int timestamp) Stores the key and val
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摘要：Given two sparse vectors, compute their dot product. Implement class SparseVector: SparseVector(nums) Initializes the object with the vector nums dotP
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摘要：(This problem is an interactive problem.) A row-sorted binary matrix means that all elements are 0 or 1 and each row of the matrix is sorted in non-de
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摘要：给一个phone pad mapping like: {1，{‘A’,'B' , 'C'}}, {2, { 'D' , 'E' , 'F' }} ... {0， {'X', 'Y', 'Z'}}. 按一次1 返回A，连续两次返回B， 连续四次重新返回A. 输入一组数字，不清楚之间间隔，返回所有可能的
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摘要：Given two strings s1 and s2, write a function to return true if s2 contains the permutation of s1. In other words, one of the first string's permutati
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