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This problem was asked by Microsoft. A number is considered perfect if its digits sum up to exactly 10. Given a positive integer n, return the n-th pe 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 1 rep 阅读全文
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This problem was asked by Google. On our special chessboard, two bishops attack each other if they share the same diagonal. This includes bishops that 阅读全文
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Given a binary tree, find the length of the longest path where each node in the path has the same value. This path may or may not pass through the roo 阅读全文
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This problem was recently asked by Google. Given a list of numbers and a number k, return whether any two numbers from the list add up to k. For examp 阅读全文
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Given an array nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see the k num 阅读全文
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This problem was asked by Google. Implement locking in a binary tree. A binary tree node can be locked or unlocked only if all of its descendants or a 阅读全文
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Implement a trie with insert, search, and startsWith methods. Notice You may assume that all inputs are consist of lowercase letters a-z. Implement a 阅读全文
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This problem was asked by Twitter. You run an e-commerce website and want to record the last N order ids in a log. Implement a data structure to accom 阅读全文
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Given an array of integers A with even length, return true if and only if it is possible to reorder it such that A[2 * i + 1] = 2 * A[2 * i] for every 阅读全文