Optimize Array Traversal to O(n) Time, O(1) Space

Problem: A standard array traversal problem where the candidate is expected to optimize the solution to O(n) time using no extra space (exact statement not preserved by the candidate).

Approach: Process the array in a single pass using only a constant number of tracking variables (running sums/counts/pointers) instead of auxiliary arrays or hashmaps, taking care to update all needed state incrementally as the single index advances, rather than doing nested passes or allocating O(n) auxiliary storage.