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A valid parentheses string is either empty , , or , where and are valid parentheses strings, and represents string concatenation. For example, , , , a 阅读全文
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Given a 2D array , each cell is 0 (representing sea) or 1 (representing land) A move consists of walking from one land square 4 directionally to anoth 阅读全文
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We are given a linked list with as the first node. Let's number the nodes in the list: etc. Each node may have a next larger value: for , is the such 阅读全文
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Given an array of s and s, consider : the i th subarray from to interpreted as a binary number (from most significant bit to least significant bit.) R 阅读全文
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Given a number , return a string consisting of s and s that represents its value in base (negative two). The returned string must have no leading zero 阅读全文
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Given a binary string (a string consisting only of '0' and '1's) and a positive integer , return true if and only if for every integer X from 1 to N, 阅读全文
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Given a positive integer , you need to find the length of the smallest positive integer such that is divisible by , and only contains the digit . Retu 阅读全文
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Given an array of positive integers, represents the value of the th sightseeing spot, and two sightseeing spots and have distance between them. The sc 阅读全文
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Given an array of integers , return if we can partition the array into three non empty parts with equal sums. Formally, we can partition the array if 阅读全文
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Given a positive integer , return the number of positive integers less than or equal to that have at least 1 repeated digit. Example 1: Input: 20 Outp 阅读全文
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A conveyor belt has packages that must be shipped from one port to another within D days. The ith package on the conveyor belt has a weight of weights 阅读全文
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You are given a list of songs where the ith song has a duration of seconds. Return the number of pairs of songs for which their total duration in seco 阅读全文
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Every non negative integer has a binary representation. For example, can be represented as in binary, as in binary, and so on. Note that except for , 阅读全文
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Return the root node of a binary search tree that matches the given traversal. (Recall that a binary search tree is a binary tree where for every node 阅读全文
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In a row of dominoes, and represent the top and bottom halves of the domino. (A domino is a tile with two numbers from 1 to 6 one on each half of the 阅读全文
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Normally, the factorial of a positive integer is the product of all positive integers less than or equal to . For example, . We instead make a clumsy 阅读全文
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Given an array of integers, we must modify the array in the following way: we choose an and replace with , and we repeat this process times in total. 阅读全文
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Given an array of 0s and 1s, we may change up to values from 0 to 1. Return the length of the longest (contiguous) subarray that contains only 1s. Exa 阅读全文
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Given a string , determine if it is valid. A string is valid if, starting with an empty string , you can transform into after performing the following 阅读全文
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Given an array of strings made only from lowercase letters, return a list of all characters that show up in all strings within the list (including dup 阅读全文
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You are given a grid of size N x N, and each cell of this grid has a lamp that is initially turned off. You are also given an array of lamp positions 阅读全文
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On an 8 x 8 chessboard, there is one white rook. There also may be empty squares, white bishops, and black pawns. These are given as characters 'R', ' 阅读全文
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We are given the node of a maximum tree: a tree where every node has a value greater than any other value in its subtree. Just as in the "previous pro 阅读全文
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In a town, there are people labelled from to . There is a rumor that one of these people is secretly the town judge. If the town judge exists, then: 1 阅读全文
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Given an array of non negative integers, the array is squareful if for every pair of adjacent elements, their sum is a perfect square. Return the numb 阅读全文
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You are given an `grid` where each cell can have one of three values: representing an empty cell, representing a fresh orange, or representing a rotte 阅读全文
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In a binary tree, the root node is at depth , and children of each depth node are at depth . Two nodes of a binary tree are cousins if they have the s 阅读全文
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Given an array of positive integers, call a (contiguous, not necessarily distinct) subarray of good if the number of different integers in that subarr 阅读全文
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On a broken calculator that has a number showing on its display, we can perform two operations: Double: Multiply the number on the display by 2, or; D 阅读全文
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Given two strings and , return the length of their longest common subsequence. A subsequence of a string is a new string generated from the original s 阅读全文
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Given an array equations of strings that represent relationships between variables, each string has length and takes one of two different forms: or . 阅读全文
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For a non negative integer , the array form of is an array of its digits in left to right order. For example, if , then the array form is . Given the 阅读全文
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Given the of a binary tree, each node has a value from to representing the letters to : a value of represents , a value of represents , and so on. Fin 阅读全文
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Given two lists of closed intervals, each list of intervals is pairwise disjoint and in sorted order. Return the intersection of these two interval li 阅读全文
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We have an array of integers, and an array of queries. For the th query , we add val to . Then, the answer to the th query is the sum of the even valu 阅读全文
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Given two integers and , return any string such that: has length and contains exactly `'a' b` letters, The substring does not occur in , and The subst 阅读全文
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In a country popular for train travel, you have planned some train travelling one year in advance. The days of the year that you will travel is given 阅读全文
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Given an array of integers , find the number of triples of indices (i, j, k) such that: `0 这道题给了一个数组，定义了一种三元组，使得这三个数字相‘与’得到为0，问有多少种不同的组合。根据题目中的例子可以发现， 阅读全文
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Create a timebased key value store class , that supports two operations. 1\. Stores the and , along with the given . 2\. Returns a value such that was 阅读全文
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On a 2 dimensional , there are 4 types of squares: represents the starting square. There is exactly one starting square. represents the ending square. 阅读全文
