How should I practice Stack Command Output?

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

Is Stack Command Output associated with Wex?

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

Problem · Stack

Stack Command Output

Learn this problem

● Easy

WexFULLTIMEPHONE SCREEN

Problem statement

Process a command string commands using an initially empty stack. Return the values removed by pop commands, in the order they are removed.

U value pushes the signed integer value onto the stack.
O removes the top value and appends it to the output.
X ends the command string. Values still on the stack are not output.

For this exercise, assume the input is valid: tokens are separated by one or more spaces, tabs, or newlines, optional whitespace may surround the string, exactly one X is the final token, and every O has a value available to pop. Integers use ordinary decimal notation with an optional leading minus sign.

Function

stackOutput(commands: String) → int[]

Examples

Example 1

commands = "U 3 U -3 O O X"return = [-3,3]

Push 3, then -3. The first pop removes -3; the second removes 3.

Example 2

commands = "U 8 O U 4 U 9 O X"return = [8,9]

The pops remove 8 and then 9. The remaining 4 is not output when X ends processing.

Constraints

1 <= commands.length <= 10^5.
There are at most 10^4 commands, including X.
Every pushed value is between -10^9 and 10^9, inclusive.
The command sequence satisfies the validity rules in the statement.