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1370. Count Number Of Nice Subarrays

Array Hash Table Math Sliding Window Prefix Sum

Problem - Count Number Of Nice Subarrays

Medium

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

Solutions

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class Solution:
    def numberOfSubarrays(self, nums: List[int], k: int) -> int:
        counter = Counter({0: 1})
        result = temp = 0
        for i in nums:
            temp += i & 1
            result += counter[temp - k]
            counter[temp] += 1
        return result

Submission Stats:

  • Runtime: 143 ms (15.28%)
  • Memory: 24.8 MB (21.42%)