Contains Duplicate
LeetcodeContains DuplicateQuestion
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 array, and it should return false if every element is distinct.
Analysis
利用hash表,将数组中的元素逐个插入hash表中,当遇到第一个重复不可插入的时候返回fa
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