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Tested Python solution for LeetCode 1248 with 16 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 1248 # by problem number
lcpy gen -s count_number_of_nice_subarrays # by problem name
nums and an integer k. A continuous subarray is called nice if there are k odd numbers on it.
Return the number of nice sub-arrays.
Input: nums = [1,1,2,1,1], k = 3
Output: 2
Explanation: The only sub-arrays with 3 odd numbers are [1,1,2,1] and [1,2,1,1].
Input: nums = [2,4,6], k = 1
Output: 0
Explanation: There are no odd numbers in the array.
Input: nums = [2,2,2,1,2,2,1,2,2,2], k = 2
Output: 16
1 <= nums.length <= 500001 <= nums[i] <= 10^51 <= k <= nums.lengthclass Solution:
# Time: O(len(nums))
# Space: O(len(nums))
def number_of_subarrays(self, nums: list[int], k: int) -> int:
prefix: dict[int, int] = {0: 1}
odds = 0
count = 0
for num in nums:
odds += num % 2
count += prefix.get(odds - k, 0)
prefix[odds] = prefix.get(odds, 0) + 1
return count
| Time | Space |
|---|---|
| O(len(nums)) | O(len(nums)) |