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Given an integer, convert it to a roman numeral. The number is guaranteed to be within the range from 1 to 3999. 4 -> IV 12 -> XII 21 -> XXI 99 -> XCI 阅读全文
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Implement a trie with insert, search, and startsWith methods. 阅读全文
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As the title described, you should only use two stacks to implement a queue's actions. The queue should support push(element), pop()and top() where po 阅读全文
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You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping yo 阅读全文
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Given an integer array, heapify it into a min-heap array. Given [3,2,1,4,5], return [1,2,3,4,5] or any legal heap array. 阅读全文
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The gray code is a binary numeral system where two successive values differ in only one bit. Given a non-negative integer n representing the total num 阅读全文
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Given n nodes labeled from 0 to n - 1 and a list ofundirected edges (each edge is a pair of nodes), write a function to check whether these edges make 阅读全文