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We start at some node in a directed graph, and every turn, we walk along a directed edge of the graph. If we reach a terminal node (that is, it has no 阅读全文
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Given n points on a 2D plane, find if there is such a line parallel to y-axis that reflect the given points symmetrically, in other words, answer whet 阅读全文
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You are given a string num, which represents a large integer. You are also given a 0-indexed integer array change of length 10 that maps each digit 0- 阅读全文
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You are given a string s consisting of lowercase English letters, and an integer k. First, convert s into an integer by replacing each letter with its 阅读全文
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You are given a string time in the form of hh:mm, where some of the digits in the string are hidden (represented by ?). The valid times are those incl 阅读全文
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You are given an n x n binary matrix grid. You are allowed to change at most one 0 to be 1. Return the size of the largest island in grid after applyi 阅读全文
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The beauty of a string is the difference in frequencies between the most frequent and least frequent characters. For example, the beauty of "abaacc" i 阅读全文
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order and str are strings composed of lowercase letters. In order, no letter occurs more than once. order was sorted in some custom order previously. 阅读全文
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You are given two positive integer arrays nums1 and nums2, both of length n. The absolute sum difference of arrays nums1 and nums2 is defined as the s 阅读全文
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A query word matches a given pattern if we can insert lowercase letters to the pattern word so that it equals the query. (We may insert each character 阅读全文
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Given a string s, return the number of unique palindromes of length three that are a subsequence of s. Note that even if there are multiple ways to ob 阅读全文
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A good meal is a meal that contains exactly two different food items with a sum of deliciousness equal to a power of two. You can pick any two differe 阅读全文
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Given the array orders, which represents the orders that customers have done in a restaurant. More specifically orders[i]=[customerNamei,tableNumberi, 阅读全文
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You are given two m x n binary matrices grid1 and grid2 containing only 0's (representing water) and 1's (representing land). An island is a group of 阅读全文
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You are given some lists of regions where the first region of each list includes all other regions in that list. Naturally, if a region X contains ano 阅读全文
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There are n bulbs that are initially off. You first turn on all the bulbs, then you turn off every second bulb. On the third round, you toggle every t 阅读全文
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Given an integer n, return true if and only if it is an Armstrong number. The k-digit number n is an Armstrong number if and only if the kth power of 阅读全文
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An n-bit gray code sequence is a sequence of 2n integers where: Every integer is in the inclusive range [0, 2n - 1], The first integer is 0, An intege 阅读全文
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A new online video game has been released, and in this video game, there are 15-minute rounds scheduled every quarter-hour period. This means that at 阅读全文
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On an N x N grid, each square grid[i][j] represents the elevation at that point (i,j). Now rain starts to fall. At time t, the depth of the water ever 阅读全文