2348. Number of Zero-Filled Subarrays

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2348. Number of Zero-Filled Subarrays

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:

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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:**

```bash
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:

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Input: nums = [2,10,2019]
Output: 0
Explanation: There is no subarray filled with 0. Therefore, we return 0.

Constraints:

  • 1 <= nums.length <= 10^5
  • -10^9 <= nums[i] <= 10^9

Hints/Notes

Solution

Language: C++

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class Solution {
public:
    // [0]: 1
    // [0, 0]: 3
    // [0, 0, 0]:
    long long zeroFilledSubarray(vector<int>& nums) {
        int n = nums.size();
        vector<long long> numZeroArrays(n + 1, 1);
        for (int i = 2; i <= n; i++) {
            numZeroArrays[i] = i + numZeroArrays[i - 1];
        }
        long long res = 0;
        for (int i = 0; i < n; ) {
            if (nums[i] == 0) {
                int start = i;
                while (i < n && nums[i] == 0) {
                    i++;
                }
                int numOfZero =  i - start;
                res += numZeroArrays[numOfZero];
            } else {
                i++;
            }
        }
        return res;
    }
};