Minimum operations needed to make array perfect

Question

Given an array of 1s and -1s the task is to make array perfect

If array satisfies below conditions then it is said to be perfect

1. all possible prefixes should have sum strictly greater than 0 and
2. all possible suffixes should have sum strictly greater than 0

The task here is to find the minimum operations required to make array perfect. Acceptable Complexity : O(N)

For Example

Consider array [1, -1, 1] there is a prefix [1,-1] whose sum is 0, same for suffix minimum operations needed to make array perfect is 1 that is make -1 into 1.

Consider array [1, 1, -1, 1, 1] No prefix or Suffix has the sum <= 0 so no modifications are needed, output 0

I've tried traversing from left to right and right to left and calculated the sum whenever sum becomes 0 i made that element 1, hope this is not the correct approach. Any idea on how this can be solved in O(N) or less.