How should I practice Run a Stack Language Interpreter?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Jane Street phone screen problems in FastPrep.

Is Run a Stack Language Interpreter associated with Jane Street?

FastPrep tags this as a Jane Street phone screen coding practice problem when the problem catalog has that company and stage context.

Run a Stack Language Interpreter

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Problem statement

Execute a simple stack program from instruction index 0 with an empty stack. Return the sequence of strings produced by PRINT, in execution order.

PUSH value pushes the entire string after the first space, including an empty string.
POP removes the top string; it does nothing on an empty stack.
PRINT appends the top string to the output without removing it; on an empty stack it appends "".
TRUNCATE k removes up to k characters from the right end of the top string. It leaves an empty string when k is at least its length, and does nothing on an empty stack.
JUMP target continues at the zero-based index target.
JUMP_IF_EMPTY target jumps when the stack is empty or its top string is empty; otherwise execution advances normally.

Every instruction other than a taken jump advances to the next index. Reaching index instructions.length ends execution. Inputs are valid and guaranteed to terminate; detecting infinite loops is unnecessary.

Function

runInterpreter(instructions: String[]) → String[]

Examples

Example 1

instructions = ["PUSH hello","PRINT","TRUNCATE 2","PRINT"]return = ["hello","hel"]

Printing preserves the top value. Truncation then removes its last two characters.

Example 2

instructions = ["PUSH ","JUMP_IF_EMPTY 4","PUSH skip","PRINT","PUSH ok","PRINT"]return = ["ok"]

The empty top value takes the jump directly to index 4, skipping the intervening instructions.

Example 3

instructions = ["POP","PRINT","PUSH abc","JUMP 5","PRINT"]return = [""]

Popping an empty stack is harmless. The first print emits an empty string, and the final jump exits the program.

Constraints

For this exercise, assume 0 <= instructions.length <= 1000 and at most 10000 executed instructions.
A pushed value has at most 50 printable ASCII characters, excluding line breaks. Its spaces are significant.
Non-PUSH operands are unsigned decimal integers. Truncation counts are at most 50; jump targets are in [0, instructions.length].
Opcodes are exactly the uppercase names above. Operand instructions have one separating space; PUSH represents an empty value. POP and PRINT have no operand.