# What is two stack PDA explain with example?

## What is two stack PDA explain with example?

A PDA with two stacks has the same computation power as for a Turing Machine….Explain Turing Machine variant Two Stack PDA?

Turing Machine | Two-stack PDA Machine |
---|---|

Change state. | Change state. |

Write a tape symbol in cell scanned. | The input symbol read. |

Move the head left or right. | Replace the symbol of each stack with a string of zero or more stack symbols. |

### What is a 2 PDA?

A 2-PDA can, by placing all a’s on stack 1, all b’s on stack 2, and then removing an a for each c read following the b’s. The language is accepted if there are no a’s remaining, and all the input has been read. Therefore, a 2-PDA is more powerful than a 1-PDA.

#### What is stack in PDA?

A pushdown automaton (PDA) is a finite automaton with a stack that has stack operations pop, push, and nop. PDAs always start with one designated symbol on the stack. A state transition depends on the input symbol and the top of the stack. The machine then performs a stack operation and enters the next state.

**What are the applications of PDA?**

Push Down Automata (PDA) – For designing the parsing phase of a compiler (Syntax Analysis). For implementation of stack applications. For evaluating the arithmetic expressions. For solving the Tower of Hanoi Problem.

**What is two stack model?**

In this data stucture, there are two stacks used hence the name two stack model. For the sake of portraying a difference, we will assume the stack will use a singly linked list as it’s underlying data structure. The idea behind this data structure is to mimic editing lines rather than a huge document.

## Does the two stack PDA simulate the computer?

Actually, a PDA with two stacks has the same computation power as a Turing Machine.

### What are the components of PDA?

PDA Components:

- Input tape: The input tape is divided in many cells or symbols.
- Finite control: The finite control has some pointer which points the current symbol which is to be read.
- Stack: The stack is a structure in which we can push and remove the items from one end only.
- Q: the finite set of states.

#### How do you write PDA?

A PDA can push an element onto the top of the stack and pop off an element from the top of the stack….This scenario can be written in the ID form as:

- δ(q0, 0, Z) = δ(q0, 0Z)
- δ(q0, 0, 0) = δ(q0, 00)
- δ(q0, 1, 0) = δ(q1, 0)
- δ(q0, 1, 0) = δ(q1, 0)
- δ(q1, 0, 0) = δ(q1, ε)
- δ(q0, ε, Z) = δ(q2, Z) (ACCEPT state)

**What are the two ways of acceptance the strings in PDA?**

PDA Acceptance

- Acceptance by Final State: The PDA is said to accept its input by the final state if it enters any final state in zero or more moves after reading the entire input.
- Acceptance by Empty Stack: On reading the input string from the initial configuration for some PDA, the stack of PDA gets empty.
- Solution:

**How do I make two stacks?**

A simple way to implement two stacks is to divide the array in two halves and assign the half space to two stacks, i.e., use arr[0] to arr[n/2] for stack1, and arr[(n/2) + 1] to arr[n-1] for stack2 where arr[] is the array to be used to implement two stacks and size of array be n.