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class Solution:
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    def subarraysWithKDistinct(self, nums: List[int], k: int) -> int:
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        return self.lengthOfLongestSubstringKDistinct(
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            nums, k
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        ) - self.lengthOfLongestSubstringKDistinct(nums, k - 1)
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    def lengthOfLongestSubstringKDistinct(self, s, k):
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        n = len(s)
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        if n * k == 0:
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            return 0
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        left = 0
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        hashmap = collections.OrderedDict()
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        subarray = 0
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        for right in range(n):
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            if s[right] in hashmap:
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                del hashmap[s[right]]
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            hashmap[s[right]] = right
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            if len(hashmap) == k + 1:
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                _, del_idx = hashmap.popitem(last=False)
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                left = del_idx + 1
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            subarray += right - left + 1
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        return subarray