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Given a non-negative integer n, count all numbers with unique digits, x, where 0 ≤ x < 10n. Example: Input: 2 Output: 91 Explanation: The answer shoul 阅读全文
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Equations are given in the format A / B = k, where A and B are variables represented as strings, and k is a real number (floating point number). Given 阅读全文
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Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and put. get(key) - Get the 阅读全文
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Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST. For this problem, a height-balanced bina 阅读全文
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Design a simplified version of Twitter where users can post tweets, follow/unfollow another user and is able to see the 10 most recent tweets in the u 阅读全文
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Given a non-negative integer num represented as a string, remove k digits from the number so that the new number is the smallest possible. Note: The l 阅读全文
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A sequence of numbers is called a wiggle sequence if the differences between successive numbers strictly alternate between positive and negative. The 阅读全文