Presum or accumulate

Binary Subarrays With Sum - LeetCode

For the problem listed above, 930. Binary Subarrays With Sum. We can use the itertools.accumulate to solve the problem as shown below. We should be careful when encountering with [0 ,0 , 0, 0] and S=0 case. As this method will fail in this case.

accumulate

Or we can use presum. Here is the code from the link below. Credit give to lee251.

[C++/Java/Python] Sliding Window, O(1) Space - LeetCode Discuss