Target Sum
问题描述（难度中等-494）You are given a list of non-negative integers, a1, a2, …, an, and a target, S. Now you have 2 symbols + and -. For each integer, you sho
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Comparator和Comparable接口
通常我们自定义的一些类需要进行比较，要用到Comparator自定义比较器传递给对应容器或者实现Comparable接口。本文主要介绍两种方式的区别。
Comparable接口Comparable是排序接口。若一个类实现了Comparable接口，就意味着该类支持排序。实现了Comparable接口
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Move Zeroes.
问题描述（难度简单-283）Given an array nums, write a function to move all 0‘s to the end of it while maintaining the relative order of the non-zero elements.
Ex
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Top K Frequent Elements
问题描述（难度中等-347）Given a non-empty array of integers, return the k most frequent elements.
Example 1:
12Input: nums = [1,1,1,2,2,3], k = 2Output: [1,2]
E
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Majority Element
问题描述（难度简单-169）Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.
You may a
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