Using recursion, find an index that cuts an array in two parts so that both parts have equal sum.
Cut means to cut like with a knife. All the cells with index <= to the result must be equal in their sum to the all the cells with index > to the result. No cells can be left off or be part of both sides.
The arrays contains arbitrary integers (i.e. positives, negatives, and zeros).
If there is no such index return -1.
You are not allowed to allocate heap objects.
You must do it in a single pass.
You must do it with recursion (i.e. cannot use loop constructs).
Can be in any language or pseudocode.
Forgot to add this: You cannot modify the array