219. Contains Duplicate II

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

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
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Intuition
To achieve linear O(N) complexity, scan from L to R.. do not sort

Save elements in a set
if set.size() > k
    remove nums[i - k - 1]

if set.contains(nums[i])
    return true

set.add(nums[i])
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Time - O(N)
Space - O(K)
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Related problems
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