1248.py

'''
1248. Count Number of Nice Subarrays
https://leetcode.com/problems/count-number-of-nice-subarrays/

Given an array of integers nums and an integer k.
A 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 is 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
'''
from typing import *

class Solution:
    def numberOfSubarrays(self, nums: List[int], k: int) -> int:
        def atMost(numOdd):
            numSubArr = left = 0
            for idx in range(len(nums)):
                numOdd -= nums[idx] % 2
                while numOdd < 0:
                    numOdd += nums[left] % 2
                    left += 1
                numSubArr += idx - left + 1
            return numSubArr

        return atMost(k) - atMost(k - 1)

#print(Solution().numberOfSubarrays(nums = [1,1,2,1,1], k = 3))
#2
print(Solution().numberOfSubarrays(nums = [2,2,2,1,2,2,1,2,2,2], k = 2))
#16
#2,2,2,1,2,2,1
#2,2,2,1,2,2,1,2
#2,2,2,1,2,2,1,2,2
#2,2,2,1,2,2,1,2,2,2
#  2,2,1,2,2,1,2,2,2
#    2,1,2,2,1,2,2,2
#      1,2,2,1,2,2,2
#      1,2,2,1,2,2
#      1,2,2,1,2
#      1,2,2,1
#    2,1,2,2,1
#    2,1,2,2,1,2
#    2,1,2,2,1,2,2
#  2,2,1,2,2,1
#  2,2,1,2,2,1,2
#  2,2,1,2,2,1,2,2