1248. Count Number of Nice Subarrays

[mah-shamim]

Discussed in #259

^{Originally posted by mah-shamim August 9, 2024}
Given an array of integers 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.

Example 1:

• 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].

Example 2:

• Input: nums = [2,4,6], k = 1
• Output: 0
• Explanation: There are no odd numbers in the array.

Example 3:

• Input: nums = [2,2,2,1,2,2,1,2,2,2], k = 2
• Output: 16

Constraints:

• 1 <= nums.length <= 50000
• 1 <= nums[i] <= 10^5
• 1 <= k <= nums.length