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Perfect Squares (M) 题目 Given a positive integer n, find the least number of perfect square numbers (for example, 1, 4, 9, 16, ...) which sum to n. Exa 阅读全文
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Merge Two Sorted Lists (E) 题目 Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of 阅读全文
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Valid Parentheses (E) 题目 Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An inp 阅读全文
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Remove Nth Node From End of List (M) 题目 Given a linked list, remove the n-th node from the end of list and return its head. Example: Given linked list 阅读全文
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4Sum (M) 题目 Given an array nums of n integers and an integer target, are there elements a, b, c, and d in nums such that a + b+ c + d = target? Find a 阅读全文