摘要：
Design a data structure that supports all following operations in average O(1) time. Note: Duplicate elements are allowed. Example: Approach #1: C++. 阅读全文
摘要：
Design a data structure that supports all following operations in average O(1) time. insert(val): Inserts an item val to the set if not already presen 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-empty array of integers, return the k most frequent elements. Example 1: Input: nums = [1,1,1,2,2,3], k = 2 Output: [1,2] Example 2: Input 阅读全文
摘要：
Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least twice in the arr 阅读全文