2348. Number of Zero-Filled Subarrays
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Given an integer array nums, return the number of subarrays filled with 0.
A subarray is a contiguous non-empty sequence of elements within an array.
Example 1:
Input: nums = [1,3,0,0,2,0,0,4] Output: 6 Explanation: There are 4 occurrences of [0] as a subarray. There are 2 occurrences of [0,0] as a subarray. There is no occurrence of a subarray with a size more than 2 filled with 0. Therefore, we return 6.
Example 2:
Input: nums = [0,0,0,2,0,0] Output: 9 Explanation: There are 5 occurrences of [0] as a subarray. There are 3 occurrences of [0,0] as a subarray. There is 1 occurrence of [0,0,0] as a subarray. There is no occurrence of a subarray with a size more than 3 filled with 0. Therefore, we return 9.
Example 3:
Input: nums = [2,10,2019] Output: 0 Explanation: There is no subarray filled with 0. Therefore, we return 0.
Constraints:
1 <= nums.length <= 105-109 <= nums[i] <= 109
Hints
Hint 1
For each zero, you can calculate the number of zero-filled subarrays that end on that index, which is the number of consecutive zeros behind the current element + 1.
Hint 2
Maintain the number of consecutive zeros behind the current element, count the number of zero-filled subarrays that end on each index, sum it up to get the answer.