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Given a string representing an expression of fraction addition and subtraction, you need to return the calculation result in string format. The final 阅读全文
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We have an array A of non-negative integers. For every (contiguous) subarray B = [A[i], A[i+1], ..., A[j]] (with i <= j), we take the bitwise OR of al 阅读全文
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Given two integers A and B, return any string S such that: S has length A + B and contains exactly A 'a' letters, and exactly B 'b' letters; The subst 阅读全文
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We are given an array A of N lowercase letter strings, all of the same length. Now, we may choose any set of deletion indices, and for each string, we 阅读全文
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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 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 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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Given the root of a binary tree, each node has a value from 0 to 25 representing the letters 'a' to 'z': a value of 0 represents 'a', a value of 1repr 阅读全文
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We have an array A of integers, and an array queries of queries. For the i-th query val = queries[i][0], index = queries[i][1], we add val to A[index] 阅读全文
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Given a binary tree, return the vertical order traversal of its nodes values. For each node at position (X, Y), its left and right children respective 阅读全文