SnowCal

SnowCal is a small programming language that keeps a single integer in memory. The program arrives as one complete list of instructions rather than a stream of individual commands. SnowCal Language Interpreter Problem Overview SnowCal is a simple coding language. It stores exactly one integer, X, in memory. The value of X always starts at 0. Available Commands The language uses the following instructions: ADD Y: Add the value Y to X. MUL Y: Multiply X by the value Y. FUN F: Start defining a new function named F. END: Finish defining the current function. INV F: Call (invoke) the function named F. Language Rules Every function has a unique name. You cannot define one function inside another (no nested functions). You can define a function but never use it. If the code contains INV F, the function F is guaranteed to exist. Your Goal: You are given a list of instructions. Run the program and return the final value of X. Important: Commands inside a function (FUN ... END) do not run immediately. They only change X when that function is called using INV. Sample Cases Case 1 Input: program = ["MUL 2", "ADD 3"] Output: 3 Explanation: X starts at 0. MUL 2: 0 * 2 equals 0. ADD 3: 0 + 3 equals 3. Case 2 Input: program = ["FUN INCREMENT", "ADD 1", "END", "INV INCREMENT", "MUL 2", "ADD 3"] Output: 5 Case 3 Input: program = ["FUN INCREMENT", "ADD 1", "END", "FUN INCREMENT2", "ADD 1", "MUL 2", "END", "MUL 2", "INV INCREMENT2", "ADD 3", "INV INCREMENT"] Output: 6 Input Limits The list of program lines is between 1 and 10,000 items long. Each line is one of the valid commands listed above. Y is an integer between -1,000,000,000 and 1,000,000,000. There are no nested functions. Notes The program is supplied as one complete list of instructions, not as a stream of individual commands. Confirm this input shape before choosing the parser state and public interface.