[LeetCode] 219. Contains Duplicate II

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

Remember the last position of each number. If find any number distinct indices difference <= k, that the answer.

class Solution:
    def containsNearbyDuplicate(self, nums: List[int], k: int) -> bool:
        seen = {}
        for i, n in enumerate(nums):
            if n in seen and i - seen[n] <= k:
                return True
            
            # update last position of 'n'
            # assume next 'n' position is j,
            # j -  the 'previous' seen[n] must larger than k
            # e.g.   previous seen[n] .... seen[n] .... j
            seen[n] = i
               
        return False