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)
}