Prefix Notation Expression Evaluation | Dataford Interview Questions

Thumbtack's quote preview may represent a calculation as a compact postfix expression, where each lowercase letter refers to a numeric value. Evaluate the expression and return its integer result.

Although the extracted example is written as ab+cd+*, this notation is postfix, not prefix: operands appear before their operators.

Formal Specification

Implement evaluate_postfix(expression, values), where expression is a non-empty string containing lowercase letters and the operators +, -, *, and /. The dictionary values maps every operand letter in the expression to an integer. Return the resulting integer.

For division, truncate toward zero. Every input expression is valid, has enough operands for every operator, and evaluates without division by zero.

Constraints

1 <= len(expression) <= 10^5
Each operand is a lowercase English letter
values contains every operand used in expression
The expression is valid postfix notation
Division by zero does not occur
Intermediate and final results fit within Python's integer range

Function Signature

def evaluate_postfix(expression, values):

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