# 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

class Solution:
    def containsNearbyDuplicate(self, nums: List[int], k: int) -> bool:
        tracker = set()
        for i,n in enumerate(nums):
            if(n in tracker):
                return True
            tracker.add(n)
            if(len(tracker)>k):
                tracker.remove(nums[i-k])
        return False