Stack • Advanced Patterns

Multiple Stacks Techniques

Certain complex problems can be elegantly solved by using two or more Stacks simultaneously to manage state, track histories, or implement Queues.

Queue using Two Stacks

You can simulate a FIFO Queue using two LIFO Stacks! One stack is the 'Input' stack. When you need to dequeue, if the 'Output' stack is empty, you pop everything from Input and push it to Output. This flips the LIFO to FIFO.

Min/Max Stack

As covered earlier, using a `main` stack for data and an `auxiliary` stack to track the minimum or maximum element at that exact state.

Text Editor Undo/Redo

Maintain an `Undo` stack and a `Redo` stack. Typing pushes to Undo. Pressing Undo pops from Undo and pushes to Redo. Pressing Redo pops from Redo and pushes to Undo.

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Stack • Advanced Patterns

Multiple Stacks Techniques

Certain complex problems can be elegantly solved by using two or more Stacks simultaneously to manage state, track histories, or implement Queues.

Queue using Two Stacks

Min/Max Stack

As covered earlier, using a `main` stack for data and an `auxiliary` stack to track the minimum or maximum element at that exact state.

Text Editor Undo/Redo

Maintain an `Undo` stack and a `Redo` stack. Typing pushes to Undo. Pressing Undo pops from Undo and pushes to Redo. Pressing Redo pops from Redo and pushes to Undo.

Multiple Stack Problems

Multiple Stack Problems

Multiple Stacks Techniques

Queue using Two Stacks

Min/Max Stack

Text Editor Undo/Redo

Multiple Stacks Techniques

Queue using Two Stacks

Min/Max Stack

Text Editor Undo/Redo