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class Solution {
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  public int subarraysWithKDistinct(int[] nums, int k) {
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    return count(nums, k) - count(nums, k - 1);
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  }
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  public int count(int[] nums, int k) {
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    HashMap<Integer, Integer> hm = new HashMap<>();
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    int left = 0, right = 0, ans = 0;
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    while (right < nums.length) {
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      hm.put(nums[right], hm.getOrDefault(nums[right], 0) + 1);
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      while (hm.size() == k + 1) {
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        hm.put(nums[left], hm.get(nums[left]) - 1);
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        if (hm.get(nums[left]) == 0) hm.remove(nums[left]);
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        left++;
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      }
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      ans += right - left + 1;
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      right++;
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    }
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    return ans;
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  }
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}