# LeetCode 219. Contains Duplicate II

## Description

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

Given an integer array `nums` and an integer `k`, return `true` if there are two distinct indices `i` and `j` in the array such that `nums[i] == nums[j]` and `abs(i - j) <= 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
```

Constraints:

• `1 <= nums.length <= 105`
• `-109 <= nums[i] <= 109`
• `0 <= k <= 105`

## Explanation

Having a dictionary to track the visited numbers and check if the element value visited and the position meets the requirement.

## Python Solution

``````class Solution:
def containsNearbyDuplicate(self, nums: List[int], k: int) -> bool:

visited = {}

for i in range(len(nums)):
if nums[i] in visited and abs(i - visited[nums[i]]) <= k:
return True

visited[nums[i]] = i

return False``````
• Time Complexity: O(N).
• Space Complexity: O(N).