Reversing an ascending integer list

Question

0.00/5 (No votes)

See more:

Hi,
I tried to reverse a list using a stack but on running the program crashes. The description of the program is in the prologue below. huff! I am tired by bugs in my programs!

/*Read a sequence of integer type and revers the list.
Input terminates as soon as integer does not exceed its predecesor and the list is printed */
#include <iostream>
#include <stack>
using namespace std;

int main()
{
    int item=1;
    stack<int> numbers; //Stack initialized to zero
    cout<<"Enter the numbers in only increasing order: "<<endl;
    while(item>numbers.top())
    {
    cin>>item;
    numbers.push(item);
    }
    cout<<endl<<endl;
    while(!numbers.empty())
    {
        cout<<numbers.top()<<" ";
        numbers.pop();
    }
}

Posted 23-Dec-10 1:36am

optimus_prime1

Updated 23-Dec-10 3:43am

Manfred Rudolf Bihy

v4

Add a Solution

Comments

Manfred Rudolf Bihy 23-Dec-10 9:44am

Edited code to clean up opening and closing tags.

4 solutions

Solution 3

From MSDN STD::stack::top[^]: The top function returns the topmost element of the stack. You should ensure that there are one or more elements on the stack before calling the top function.

Although your stack does exist it does not contain any entries, so a call to top() will throw an exception; and since you are not in a try{}/catch{} block your program crashes. If you change your while{} to a do{}/while{} you can ensure that the stack will always have at least one value before doing the test.

Posted 23-Dec-10 2:26am

Richard MacCutchan

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

johannesnestler · Accepted Answer · 2010-12-23T02:36:00

Hi,

As Richard mentioned (in between) add items to the stack before calling top - there was another bug (changed order)

C++

#include <iostream>
#include <stack>

using namespace std;

int main()
{
    int item = 1;
    stack<int> numbers;
    numbers.push(0); // push a first item on the stack or top() will fail
    cout << "Enter the numbers in only increasing order : " << endl;

    while(item > numbers.top())
    {
        numbers.push(item); // changed order!
        cin >> item;        // -"-
    }

    cout<<endl<<endl;
    while(!numbers.empty())
    {
        cout << numbers.top() << " ";
        numbers.pop();
    }
}

Manfred Rudolf Bihy · Accepted Answer · 2010-12-23T03:52:00

Why not like this:

C++

#include <iostream>
#include <stack>

using namespace std;

int main()
{
    int lastItem = -1; //Since you start with 1 anyway -1 will be smaller from the start in the condition of the while statment
    int item = 1;
    stack<int> numbers;
    
    cout << "Enter the numbers in only increasing order :   " << endl;

    cin >> item;        // Read first number here
    while(item > lastItem) // proceed only if input was larger than last input
    {
        numbers.push(item);       // changed order!
        lastItem = item;        
        cin >> item;
    }

    cout<<endl<<endl;
    while(!numbers.empty())
    {
        cout << numbers.top() << " ";
        numbers.pop();
    }
}

That should do it! Unless of course you'd also wanted to enter negative numbers. But as an added bonus you wont get any extra elements you had not explicitely entered.

Cheers,

Manfred

#realJSOP · Accepted Answer · 2010-12-23T01:38:00

Solution 1

Have you tried - oh, I don't know - running it under the debugger?

Posted 23-Dec-10 1:38am

#realJSOP

Comments

optimus_prime1 23-Dec-10 7:40am

It crahes as soon as run this. (using CodeBlocks)

Reversing an ascending integer list

4 solutions

Solution 3

Solution 4

Solution 5

Solution 1

Add your solution here

Preview 0