class Solution:
def containsNearbyDuplicate(self, nums: 'List[int]', k: 'int') -> 'bool':
position = {}
for index, num in enumerate(nums):
if num not in position:
position[num] = []
position[num].append(index)
for indexes in position.values():
for i in range(len(indexes) - 1):
if indexes[i+1] - indexes[i] <= k:
return True
return False