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题目： A 3 x 3 magic square is a 3 x 3 grid filled with distinct numbers from 1 to 9 such that each row, column, and both diagonals all have the same sum 阅读全文
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题目： Given a linked list, determine if it has a cycle in it. 给定一个链表，确定它是否有一个循环。 Follow up:Can you solve it without using extra space? 你能不用额外的空间解决它吗？ 解答 阅读全文
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题目： Design a HashSet without using any built-in hash table libraries. 在不使用任何内置哈希表库的情况下设计HashSet。 To be specific, your design should include these func 阅读全文
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题目： Given two strings s and t, determine if they are isomorphic. 给定两个字符串s和t，确定它们是否是同构的。 Two strings are isomorphic if the characters in s can be repla 阅读全文