Use a two-pointer approach with prefix sums to find the split points in one pass for dividing an array into three equal-sum parts.

The two-pointer method is essentially the same as the prefix sum approach described above. Compute the total sum and verify it is divisible by 3. Then iterate once, keeping a running sum. The first time the running sum equals target (total/3) mark the first cut; the next time it equals 2*target mark the second cut. If both cuts are found before the last element, the array can be split. The algorithm runs in O(n) time, uses O(1) extra space, and correctly handles negative values. The key insight is that the cumulative sum at the second cut must be exactly twice the target, guaranteeing that the remaining suffix also sums to the target.