Reason About Alternating Positive and Negative Values

# Reason About Alternating Positive and Negative Values Given an array containing positive and negative values, explain how to rearrange it so adjacent returned values alternate in sign. Before choosing an algorithm, identify the ordering and leftover-value rules that the source leaves open. ### Constraints & Assumptions - The source mentions positive and negative values but does not define how zero is classified. - The counts of the two signs may differ. - The source does not require stability or identify which sign appears first. ### Clarifying Questions to Ask - Must the output begin with a positive value, a negative value, or whichever sign is more frequent? - Must relative order within each sign be preserved? - How should zeros and unmatched values be handled when strict alternation can no longer continue? ```hint Count before arranging The achievable alternating prefix and any leftover suffix depend on the two sign counts and the chosen starting rule. ``` ### What a Strong Answer Covers - Recognition that several arrays can satisfy the same alternation property. - Stable and in-place algorithm options with their space trade-offs. - Explicit zero, starting-sign, and unequal-count behavior. - Complexity and tests for balanced, imbalanced, all-one-sign, and duplicate values. ### Follow-up Questions 1. When is strict alternation impossible without discarding values? 2. How would the approach change if the rearrangement had to be stable and in place?