2432. Number Of Zero Filled Subarrays¶

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2432. 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

Solution¶

class Solution {
    public long zeroFilledSubarray(int[] nums) {
        int n = nums.length;
        int prev = -1, current = -1;
        long count = 0;
        for (int i = 0; i < n; i++) {
            if (nums[i] != 0) {
                if (prev == -1) continue;
                int len = current - prev + 1;
                current = -1; prev = -1;
                count += (len * 1L * (len + 1)) / 2;
            }
            if (nums[i] == 0) {
                if (prev == -1) {
                    prev = i;
                    current = i;
                }
                else 
                    current = i;
            }
        }      
        if (prev != -1) {
            int len = n - prev;
            count += (len * 1L * (len + 1)) / 2;
        }
        return count;
    }
}

Complexity Analysis¶

• Time Complexity: O(?)
• Space Complexity: O(?)

Approach¶

Detailed explanation of the approach will be added here