RPN-like Calculator VM | Dataford Interview Questions

Process a string containing numbers and operators: + - * /, plus "swap", "dup" (duplicate), "pop", "drop". (Full operator spec hidden; visible test cases include ('-5 3 + .', [-2]), ('1 . 2 . 3 . 4', [1, 2, 3]), ('99 2 3 + .', [5]), ('1 2 drop .', [1]), ('20 5 / .', [4]), ('30 3 / 4 - .', [6]).)

Asked in the tech phone screen 1 stage. Hand-written Python, no AI suggestions allowed; must handle negative number tokens like -5.

Implement evaluate(program). Tokens are separated by whitespace. Numbers are pushed onto a stack. Arithmetic operators pop the right operand first, then the left operand, and push the result. swap exchanges the top two values, dup copies the top value, pop removes the top value, drop is an alias for removing the top value, and . removes the top value and appends it to the output. Division truncates toward zero. Return the output list in evaluation order. Inputs are valid and never underflow the stack.

Constraints

1 <= number of tokens <= 10^4
Each numeric token represents a signed 32-bit integer
Tokens are separated by one or more whitespace characters
The program is valid and never performs an operation on an insufficient stack
Division operands are nonzero
Division truncates toward zero

Function Signature

def evaluate(program):

Your question is RPN-like Calculator VM. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

Asked in the tech phone screen 1 stage. Hand-written Python, no AI suggestions allowed; must handle negative number tokens like -5.

Constraints

1 <= number of tokens <= 10^4
Each numeric token represents a signed 32-bit integer
Tokens are separated by one or more whitespace characters
The program is valid and never performs an operation on an insufficient stack
Division operands are nonzero
Division truncates toward zero

Function Signature

def evaluate(program):

Your question is RPN-like Calculator VM. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.