930. Binary Subarrays With Sum

In an array A of 0s and 1s, how many non-empty subarrays have sum S?

Example 1:

Input: A = [1,0,1,0,1], S = 2
Output: 4
Explanation:
The 4 subarrays are bolded below:
[ **1,0,1** ,0,1]
[ **1,0,1,0** ,1]
[1, **0,1,0,1** ]
[1,0, **1,0,1** ]

Note:

1. A.length <= 30000
2. 0 <= S <= A.length
3. A[i] is either 0 or 1.

# @lc code=start
using LeetCode

function num_subarrays_with_sum(nums::Vector{Int}, goal::Int)
    cnt = OffsetArray(fill(0, length(nums) + 1), -1)
    s, res = 0, 0
    for num in nums
        cnt[s] += 1
        s += num
        res += get(cnt, s - goal, 0)
    end
    res
end
# @lc code=end

num_subarrays_with_sum (generic function with 1 method)

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