LeetCode 930. Binary Subarrays With Sum

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题型，会了1道，其他的基本都会了。

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.