219. 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 difference between i and j is at most k.

巧妙地利用字典

class Solution(object):
    def containsNearbyDuplicate(self, nums, k):
        """
        :type nums: List[int]
        :type k: int
        :rtype: bool
        """
        dictionary={}
        for key,value in enumerate(nums):
            if value in dictionary and key-dictionary[value]<=k:
                return True
            dictionary[value]=key
        return False