Find All Subarrays With a Given Sum

Question

## Problem

Count contiguous subarrays summing to a target (array may contain negatives).

## Example
```
[1,2,3], target=3 -> 2 ([1,2],[3])
```

## Constraints
- 1 ≤ n ≤ 10^4

## Approach
Prefix-sum + hash map.