# Evaluate a Variadic Addition or Subtraction Expression Implement an evaluator for an array whose first element is an operator and whose remaining elements are integer operands. - `"+"` returns the sum of every operand. - `"-"` starts with the first operand and subtracts each later operand from left to right. For example: ```text ["+", 1, 2, 3] -> 6 ["-", 10, 5, 3] -> 2 ``` Return the computed integer. ### Constraints & Assumptions - The expression contains a supported operator followed by at least one integer. - Do not reorder operands; subtraction is left-associative. - The core implementation only needs to support addition and subtraction. ### Clarifying Questions to Ask - Should a one-operand subtraction expression return that operand or its negation? - How should an unsupported operator be reported? - If multiplication and division are added, should this array remain a single variadic operation or support nested expressions and precedence? ```hint Identify the accumulator seed Addition can start from its identity, but left-associative subtraction needs the first operand as its initial accumulator. ``` ```hint Separate dispatch from iteration Choose the operation once, then process the operands without checking the operator on every branch of the loop. ``` ### Evaluation Criteria - Correct handling of variadic addition and left-associative subtraction. - A clear empty or malformed-input policy instead of an accidental index error. - A design that can add operators without duplicating the traversal logic. - Linear time in the number of operands and constant auxiliary space. ### Extensions to Discuss - Where would you add multiplication and division support? - What division-by-zero and integer-versus-floating-point rules would the extended evaluator need? - How would the representation change if expressions could be nested?