2348

2348. Number of Zero-Filled Subarrays (Medium)

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

Companies: Google

Related Topics:
Array, Math

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Solution 1.

// OJ: https://leetcode.com/problems/number-of-zero-filled-subarrays
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(1)
class Solution {
public:
    long long zeroFilledSubarray(vector<int>& A) {
        long long ans = 0, N = A.size();
        for (int i = 0; i < N; ++i) {
            if (A[i] != 0) continue;
            long long cnt = 1;
            while (i + 1 < N && A[i + 1] == 0) ++i, ++cnt;
            ans += cnt * (1 + cnt) / 2;
        }
        return ans;
    }
};