Contains Duplicate II

　　　　这道题为简单题

　　题目：

　　　　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.

　　思路：

　　　　利用字典，如果该元素存在于字典中，就判断是否这两个的索引值的绝对值是否小于等于k，如果没有小于就添加或更改字典的键值

　　代码：

class Solution(object):
    def containsNearbyDuplicate(self, nums, k):
        """
        :type nums: List[int]
        :type k: int
        :rtype: bool
        """
        b = {}
        for i in range(len(nums)):
            if nums[i] in b and abs(b[nums[i]] - i) <= k:
                    return True
            b[nums[i]] = i
        return False