CSCI 340 Computer Assignment 4 Spring 2018

(10 points)

For this computer assignment, you are to implement the Queue class using STL stacks.

Queue.h contains the definition of the Queue class. It is given here to facilitate

the following description:

class Queue {

private:

std::stack s1, s2;

public:

bool empty() const;

int size() const;

int front();

int back();

void push(const int& val);

void pop();

};

You are required to implement this class in assignment4.cc. In this file, the main

function is already provided. The driver program works with an input file

assignment4input.txt.

In the implementation of the class, you are going to use stacks s1 and s2 to store and

manipulate data. You are suggested to use only s1 to save the element just pushed in

(i.e. enqueueed), and use s2 to hold older elements. More details are described below.

empty() : You need to make sure both s1 and s2 are empty.

size() : You need to count the number of elements in both s1 and s2.

front(): This method returns the oldest element. First of all if s2 is empty, move

all elements from s1 to s2. Simply return the top element in s2.

back(): This method returns the newest element. Simply return the top element

in s1.

push(): Simply add the element to s1.

pop(): This method removes the oldest element. You can reuse the method

front().

Use the following provided main, make sure to add your functions here:

#include

#include

#include "Queue.h"

using namespace std;

int main() {

Queue q;

string op;

int val = 0;

cout << "operation -- size front end" << endl;

cin >> op;

while ( !cin.eof() ) {

if ( op == "push" ) {

cin >> val;

q.push( val );

cout << op << " " << val << " -- ";

}

else if ( op == "pop" ) {

q.pop();

cout << op << " -- ";

}

else {

cerr << "Error input: " << op << endl;

return 1;

}

cout << setw(3) << q.size() << setw(5) << q.front() << setw(5) << q.back() << endl;

cin >> op;

}

while ( !q.empty() )

q.pop();

return 0;

}

Use Input txt:

push 1

push 2

push 3

push 4

pop

push 5

push 6

push 7

pop

push 8

push 9

Your output should look like this:

operation -- size front end

push 1 -- 1 1 1

push 2 -- 2 1 2

push 3 -- 3 1 3

push 4 -- 4 1 4

pop -- 3 2 4

push 5 -- 4 2 5

push 6 -- 5 2 6

push 7 -- 6 2 7

pop -- 5 3 7

push 8 -- 6 3 8

push 9 -- 7 3 9