How do I am getting error for removing middle element from stack

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void add(stack<int>& inputStack, int N, int data, vector<int>& ans, int total, stack<int>& tempStack) {
    if (data <= 0) {
        return;
    }
    
    inputStack.push(ans[data - 1]);
    add(inputStack, N, data - 1, ans, total, tempStack);
}

void remove(stack<int>& inputStack, int N, int data, vector<int>& ans, stack<int>& tempStack) {
    int mid = (N) / 2;
    if (data <= 0) {
        inputStack.pop();
        return;
    }
    
    ans.push_back(inputStack.top());
    inputStack.pop();
    remove(inputStack, N, data - 1, ans, tempStack);
}

void deleteMiddle(stack<int>& inputStack, int N) {
    int data = (N) / 2;
    vector<int> ans(data);
    stack<int> tempStack;
    remove(inputStack, N, data, ans, tempStack);
   
    int total = 0;
    data = (N) / 2;
    add(inputStack, N, data, ans, total, tempStack);
}

What I have tried:

I have tried using recursion.
It is showing error for testcase like 1 2 3 4 5
Mine output:
0 0 4 5?
could anybody explain why is it showing error?

Posted 12-Aug-23 17:51pm

I RAJ

Updated 13-Aug-23 6:23am

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OriginalGriff · Answer 1 · 2023-08-12T18:52:00

Compiling does not mean your code is right! :laugh:
Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.

So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.

Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:

Input   Expected output    Actual output
  1            2                 1
  2            4                 4
  3            6                 9
  4            8                16

Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:

C++

int Double(int value)
   {
   return value * value;
   }

Once you have an idea what might be going wrong, start using the debugger to find out why. Put a breakpoint on the first line of the method, and run your app. When it reaches the breakpoint, the debugger will stop, and hand control over to you. You can now run your code line-by-line (called "single stepping") and look at (or even change) variable contents as necessary (heck, you can even change the code and try again if you need to).
Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?
Hopefully, that should help you locate which part of that code has a problem, and what the problem is.
This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!

OriginalGriff · Answer 2 · 2023-08-13T06:23:00

Just as an aside, I took your task, and implemented it in C# (so you can't hand it in as your own work) because your C++ implementation is ... ummm ... wierd.
Here's the class that does all the work:

using System;
using System.Collections.Generic;
using System.Linq;

namespace OneOffJobs
    {
    public class DebugStack : Stack<int>
        {
        #region Constructors
        public DebugStack(IEnumerable<int> data)
            {
            foreach (int x in data) Push(x);
            }

        #endregion

        #region Public Methods
        public List<int> Remove(int n)
            {
            List<int> ans = new List<int>();
            while (n-- > 0) { ans.Add(Pop()); }
            return ans;
            }
        public int DeleteMiddle()
            {
            if (Count == 0) return int.MinValue;
            int data = Count / 2;
            Stack<int> ans = new Stack<int>();
            while (data-- >= 0) ans.Push(Pop());
            int returnValue = ans.Pop();
            foreach (int x in ans) Push(x);
            return returnValue;
            }
        #endregion

        #region Overrides
        public override string ToString()
            {
            return string.Join(", ", this.Reverse());
            }
        #endregion
        }
    }

And the calling code is clean as well:

DebugStack ds = new DebugStack(new int[] {1, 2, 3, 4, 5});
Console.WriteLine(ds.ToString());
ds.DeleteMiddle();
Console.WriteLine(ds.ToString());
ds.Remove(2);
Console.WriteLine(ds.ToString());

That's the advantage of understanding how a language works: instead of trying to force "built in classes" to do what you want, you use what they can do properly. In this case, the class derives from Stack<int> so it inherits useful methods like Push and Pop automatically. Your code shows that you don't understand C++ classes very well, and to get you to this kind of exercise, you really should by now!

I'd suggest that you throw away the code you have, and start again using the stack and vector constructs intelligently. You will get better code, and that should mean a better grade.

How do I am getting error for removing middle element from stack

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