Question

the purpose of the code is to implement a stack

how can i convert this code in a way that these changes apply to it?

// simplify the logic of the main

// getline(cin, line) needs to be changed to a normal cin >> line;

//make a function for 'list'

// not allowed temporary stack (stack s2)

//merge the catches (errors)

// introduce another function for main

// avoid repetitive code

here is the code:

#include

#include

#include

#include

#include

using namespace std;

class Stack {

    public:

        bool isEmpty();

        int top();

        int pop();

        void push(int);

    private:

        vector elements;

};

bool Stack::isEmpty() {

    return elements.empty();

}

int Stack::top() {

    if(isEmpty()) {

        throw runtime_error("error: stack is empty");

    }

    else {

        return elements.back();

    }

}

int Stack::pop() {

    if(isEmpty()) {

        throw runtime_error("error: stack is empty");

    }

    else {

        int item = elements.back();

        elements.pop_back();

        return item;

    }

}

void Stack::push(int item) {

    elements.push_back(item);

}

int main() {

    string line, cmd;

    int val;

    Stack stack;

    cout << "stack> " << endl;

    while(getline(cin, line)) {

        if(line.find_first_not_of(" \t") == string:: npos) {

            cout << "stack> ";

            continue;

        }

        line = line.substr(line.find_first_not_of(" \t"));

        cmd = line.substr(0, line.find(" "));

        if(cmd == "push") {

            try {

                line = line.substr(line.find(" ") + 1);

                if(line.size() == 0 || line.at(0) == '-' || line.at(0) == '+' && line.find_first_of("0123456789") > 1 || line.find_first_not_of("0123456789+-") == 0) {

                    throw runtime_error("error: not a number");

                }

            

                else {

                    val = atoi(line.c_str());

                    stack.push(val);

                }

            }

            catch(runtime_error& excpt) {

                cout << excpt.what() << endl;

            }

        }

        else if(cmd == "pop") {

            try {

                val = stack.pop();

                cout << val << endl;

            }

            catch(runtime_error& excpt) {

                cout << excpt.what() << endl;

            }

        }

        else if(cmd == "top") {

            try {

                val = stack.top();

                cout << val << endl;

            }

            catch(runtime_error& excpt) {

                cout << excpt.what() << endl;

            }

        }

        else if(cmd == "list") {

            Stack s2;

            bool first = true;

            cout << "[";

            while(!stack.isEmpty()) {

                val = stack.pop();

                s2.push(val);

                if(!first) {

                    cout << ",";

                }

                cout << val;

                first = false;

            }

            cout << "]" << endl;

            while(!s2.isEmpty()) {

                stack.push(s2.pop());

            }

        }

        else if(cmd == "end") {

            break;

        }

        else {

            cin.ignore(numeric_limits::max(), '\n');

            cout << "error: invalid command" << endl;

        }

        cout << "stack> " << endl;

    }   

}

Answer 1

#include <bits/stdc++.h>
using namespace std;

// Declare linked list node

struct Node {
   int data;
   struct Node* link;
};
struct Node* top;

// Utility function to add an element data in the stack
// insert at the beginning
void push(int data)
{
   // create new node temp and allocate memory
   struct Node* temp;
   temp = new Node();

   // check if stack (heap) is full. Then inserting an element would
   // lead to stack overflow
   if (!temp) {
       cout << "\nHeap Overflow";
       exit(1);
   }

   // initialize data into temp data field
   temp->data = data;

   // put top pointer reference into temp link
   temp->link = top;

   // make temp as top of Stack
   top = temp;
}

// Utility function to check if the stack is empty or not
int isEmpty()
{
   return top == NULL;
}

// Utility function to return top element in a stack
int peek()
{
   // check for empty stack
   if (!isEmpty())
       return top->data;
   else
       exit(1);
}

// Utility function to pop top
// element from the stack

void pop()
{
   struct Node* temp;

   // check for stack underflow
   if (top == NULL) {
       cout << "\nStack Underflow" << endl;
       exit(1);
   }
   else {
       // top assign into temp
       temp = top;

       // assign second node to top
       top = top->link;

       // destroy connection between first and second
       temp->link = NULL;

       // release memory of top node
       free(temp);
   }
}

// Function to print all the
// elements of the stack
void display()
{
   struct Node* temp;

   // check for stack underflow
   if (top == NULL) {
       cout << "\nStack Underflow";
       exit(1);
   }
   else {
       temp = top;
       while (temp != NULL) {

           // print node data
           cout << temp->data << " ";

           // assign temp link to temp
           temp = temp->link;
       }
   }
}
int main()
{
   // push the elements of stack
   push(11);
   push(22);
   push(33);
   push(44);
   // display stack elements
   display();
   // print top elementof stack
   cout << "\nTop element is\n" << peek();
   pop();
   cout<<"\n";
   cout<<"After poping stack elements are\n";
   display();
   cout << "\nTop element is\n" << peek();
   return 0;
}