Description
Given an integer array nums
and an integer k
, return the number of good subarrays of nums
.
A good array is an array where the number of different integers in that array is exactly k
.
- For example,
[1,2,3,1,2]
has3
different integers:1
,2
, and3
.
A subarray is a contiguous part of an array.
Example 1:
Input: nums = [1,2,1,2,3], k = 2 Output: 7 Explanation: Subarrays formed with exactly 2 different integers: [1,2], [2,1], [1,2], [2,3], [1,2,1], [2,1,2], [1,2,1,2]
Example 2:
Input: nums = [1,2,1,3,4], k = 3 Output: 3 Explanation: Subarrays formed with exactly 3 different integers: [1,2,1,3], [2,1,3], [1,3,4].
Constraints:
1 <= nums.length <= 2 * 104
1 <= nums[i], k <= nums.length
Solution
Python3
class Solution:
def subarraysWithKDistinct(self, nums: List[int], k: int) -> int:
N = len(nums)
# exact(k) = atMost(k) - atMost(k - 1)
def atMost(k):
counter = Counter()
res = i = count = 0
for j, x in enumerate(nums):
if counter[x] == 0:
count += 1
counter[x] += 1
while count > k:
counter[nums[i]] -= 1
if counter[nums[i]] == 0:
count -= 1
i += 1
res += j - i - 1
return res
return atMost(k) - atMost(k - 1)