LeetCode219 Contains Duplicate II

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本文介绍了一个算法问题，即如何在一个整数数组中找到是否存在两个不同的索引 i 和 j，使得 nums[i]=nums[j] 并且 i 和 j 的绝对差不超过 k。通过使用 HashSet 数据结构，我们实现了高效的解决方案。

题目：

Given an array of integers and an integer k, find out whether there are two distinct indices iand j in the array such that nums[i] = nums[j] and the absolute difference between i and j is at most k.

Example 1:

Input: nums = [1,2,3,1], k = 3

Output: true

Example 2:

Input: nums = [1,0,1,1], k = 1

Output: true

Example 3:

Input: nums = [1,2,3,1,2,3], k = 2

Output: false

public class ContainsDuplicateII {
    public boolean containsNearbyDuplicate(int[] nums, int k) {
        Set<Integer> record = new HashSet<>();
        for (int i = 0; i < nums.length; i++) {
            if (record.contains(nums[i]))
                return true;
            record.add(nums[i]);
            if (record.size() == k + 1){
                record.remove(nums[i - k]);
            }
        }
        return false;
    }

    public static void main(String[] args) {
        int[] nums = { 1,2,3,1,2,3 };
        int k = 2;
        System.out.println(new ContainsDuplicateII().containsNearbyDuplicate(nums, k));
    }
}