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description:

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

Solution:

class Solution {
 public:
  long long zeroFilledSubarray(vector<int>& nums) {
    long long ans = 0;
    int indexBeforeZero = -1;

    for (int i = 0; i < nums.size(); ++i)
      if (nums[i])
        indexBeforeZero = i;
      else
        ans += i - indexBeforeZero;

    return ans;
  }
};

Leetcode

challenge

Here is the link for the problem:
https://leetcode.com/problems/number-of-zero-filled-subarrays/