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 <= 10^5

• -10^9 <= nums[i] <= 10^9

解題

這篇 的解釋很詳細

func zeroFilledSubarray(nums []int) int64 {
    ans := 0
    curcount := 0
    cur := 1

    for _, n := range nums {
        if n != 0 {
            ans += curcount 
            curcount = 0
            cur = 1
        } else {
            curcount += cur
            cur++
        }
    }

    ans += curcount 

    return int64(ans)
}