# 219.Contains-Duplicate-II

## 219. Contains Duplicate II

## 题目地址

<https://leetcode.com/problems/contains-duplicate-ii/>

## 题目描述

```
Given an array of integers and an integer k, find out whether there are two distinct indices i and 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
```

## 代码

### Approach #1 Naive Linear Search

```java
class Solution {
    public boolean containsNearbyDuplicate(int[] nums, int k) {
        for (int i = 0; i < nums.length; i++) {
        for (int j = i + 1; j < Math.min(i + k + 1, nums.length); j++) {
          if (nums[i] == nums[j])    return true;
        }
      }
      return false;
    }
}
```

### Approach #2 (Hash Table)

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


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