Transfer One Stack Into the Other

StackQueue fakes a queue out of two stacks: enqueue pushes onto inbox, while dequeue and peek take from outbox, which holds values already flipped into arrival order. Both call transfer() first, and only transfer() is missing.

Requirements:
1. Do nothing at all while outbox still holds values.
2. Only when outbox is empty, pop every value off inbox and push it onto outbox.

Do NOT write a main method.

Expected Output:

1↵
2↵
3↵
4↵
-1↵

= newline. The output ends with a newline — print one after the last line.

Hints2 available

Topics:

Data Structures & AlgorithmsQueues

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