Given a binary array?nums?and an integer?goal, return?the number of non-empty?subarrays?with a sum?goal.

A?subarray?is a contiguous part of the array.

?

Example 1:

Input: nums = [1,0,1,0,1], goal = 2

Output: 4

Explanation:?

The 4 subarrays are bolded and underlined below:?

[1,0,1,0,1]

[1,0,1,0,1]?

[1,0,1,0,1]?

[1,0,1,0,1]

Example 2:

Input: nums = [0,0,0,0,0], goal = 0

Output: 15

?pre_sum題型，會了1道，其他的基本都會了。

Constraints:

• 1 <= nums.length <= 3 * 104

• nums[i]?is either?0?or?1.

• 0 <= goal <= nums.length

Runtime:?2241 ms, faster than?5.07%?of?Java?online submissions for?Binary Subarrays With Sum.

Memory Usage:?47 MB, less than?41.47%?of?Java?online submissions for?Binary Subarrays With Sum.