Solution: Implement Two Stacks Using One Array

Statement

Design a data structure TwoStacks, that represents two stacks using a single list, where both stacks share the same list for storing elements.

The following operations must be supported:

• push1(value): Takes an integer value and inserts it into the first stack.

• push2(value): Takes an integer value and inserts it into the second stack.

• pop1(): Removes the top element from the first stack and returns it.

• pop2(): Removes the top element from the second stack and returns it.

Note: Perform all operations in-place without resizing the underlying list, maintaining a fixed size throughout.

Constraints:

• $1 \leq$ list.length $\leq 10^3$ ...