Trouble with bubble sort?

In this program i am writing to a file, reading the values to a array and then sort it based on id which is a char. Got it to read and write but need help with sorting it.
Here is the code:

Code:

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#include <stdio.h>
#include <iostream.h>
#include <conio.h>
#include <fstream.h>
#include <string.h>
#include <stdlib.h>


class person
{
  public: char id[5];
/*          char name[15];
          char age[5];
          char address[15];*/
          char buffer[50];
};
fstream val,file;
person p;
char id[5];
void write()
{
 val.open("person4.txt",ios::in);
 if(!val)
 {
  cout << "Cannot open file" << endl;
  exit(1);
 }

 cout << "Enter ID: " ;
 cin >> id;

while(!val.eof())
 {
  val.getline(p.id,5,'|');
  if(strcmp(id,p.id)==0)
    {
      cout << "ID already exists" << endl;
      val.close();
      getch();
      return;

    }
 }
 val.close();
 strcpy(p.id,id);
 file.open("person4.txt",ios::app);
 if(!file)
 {
 cout << "Cannot open file" << endl;
 exit(1);
 }
/* cout << "Enter name: " ;
 cin >> p.name;
 cout << "Enter age: ";
 cin >> p.age;
 cout << "Enter address: ";
 cin >> p.address;*/
 strcpy(p.buffer,p.id);
 strcat(p.buffer,"|");
/* strcat(p.buffer,p.name);
 strcat(p.buffer,"|");
 strcat(p.buffer,p.age);
 strcat(p.buffer,"|");
 strcat(p.buffer,p.address);
 strcat(p.buffer,"!"); */
 strcat(p.buffer,"\n");
 file << p.buffer;
 file.close();
}
void display()
{
 int i,n;
 person p[20];
 char* temp;//temp[20];


 file.open("person4.txt",ios::in);
 if(!file)
 {
  cout << "Cannot open file!" << endl;
  getch();
  exit(1);
 }
 n=0;
 i=0;
 cout << "ID\t\tName\t\tAge\t\tAddress" << endl;
 cout << "....\t\t..\t\t...\t\t..." << endl;
 while(!file.eof())
 {


  file.getline(p[i].id,5,'|');
  cout<<"p[i] id and i value"<<i<<p[i].id<<endl;
  //file.getline(p[i].name,15,'|');
  //file.getline(p[i].age,5,'|');
  //file.getline(p[i].address,15,'!');
  i++;
  n++;

 }

 file.close();

  for(int j=0;j<n;j++)
    {
      for(int k=j+1;k<n;k++)
      {
            if(strcmp(p[j].id,p[k].id)>= 0)
            {
              strcpy(temp,p[k].id);//(temp[j],p[k].id);
             
              strcpy(p[k].id,p[j].id);
              strcpy(p[j].id,temp);//(p[j].id,temp[k]);
            }
      }
    }


for(i=0;i<n;i++)
        cout<<p[i].id<<endl;


// file.close();
 getch();
}

void main()
{

 int choice;

 while(1)
 {
  clrscr();
  cout << "0: Exit: " << endl;
  cout << "1: Write: " << endl;
  cout << "2: Display: " << endl;
  cin >> choice;

  switch(choice)
  {
  case 0: exit(0);
  break;
  case 1: write();
  break;
  case 2: display();
  break;
  default: cout << "invalid";
  break;

  }

 }

}

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Code:

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char* temp;//temp[20];

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*temp is not correct here as no memory allocation is done so the contents of temp are unknown and data is copied to this address! char temp[20] provides the required memory.

Why are you using iostream.h and fstream.h? This is not standard c++. Also why are you using c-style strings instead of the c++ string class?

Is this a homework exercise?

Using turbo c++ and yes this is a homework where they said i have to use turbo or else this would be much easier on visual c++

You are not being taught the right way in using c++. :thumbd: When learning c++, you should be taught the correct c++ way of doing things. Your code is not even standard c++.

Quote:

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Got it to read and write

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The read function is not correct. When you write, you write a newline at the end of each line. When you read, you are reading using

Code:

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file.getline(p[i].id, 5, '|');

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which will read chars until either | is read or eof is reached. As a line ends with a newline, this is read as the first part of the next read chars - which is incorrect. If you want to read like this, you need to remove the newline from the beginning of the read chars if one is present.

For one way this could be written as c++, consider the code below. Note how it looks quite different to the code in post #1. IMO this is how you should be being taught to code with c++.

Code:

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#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
#include <map>
using namespace std;

const char delim = '|';
const string filname = "person4.txt";

class person
{
private:
        string id;
        string name;
        string age;
        string address;

public:
        person() {}

        person(const string& aid, const string& aname, const string& aage, const string& aaddress) : id(aid), name(aname), age(aage), address(aaddress) {}

        string getid() const
        {
                return id;
        }

        void display() const;

        friend bool operator<(const person& lp, const person& rp);
        friend istream& operator>> (istream& is, person& per);
        friend ostream& operator<<(ostream& os, const person& per);
};

class people {
private:
        map<string, person> mp;

public:
        bool read(const string& fnam);
        void display() const;
        bool insert(const person& per);
        bool write(const string& fnam) const;
};

bool operator<(const person& lp, const person& rp)
{
        return lp.id < rp.id;
}

void person::display() const
{
        cout << id << " " << name << " " << age << " " << address << endl;
}

istream& operator>> (istream& is, person& per)
{
        string line;

        if (getline(is, line)) {
                stringstream ss(line);
                string str;

                getline(ss, str, delim);
                per.id = str;

                getline(ss, str, delim);
                per.name = str;

                getline(ss, str, delim);
                per.age = str;

                getline(ss, str, delim);
                per.address = str;
        }

        return is;
}

ostream& operator<< (ostream& os, const person& per)
{
        return os << per.id << delim << per.name << delim << per.age << delim << per.address << delim;
}

bool people::insert(const person& per)
{
        return mp.insert(pair<string, person>(per.getid(), per)).second;
}

bool people::write(const string& fnam) const
{
        ofstream ofs(fnam);

        if (!ofs.is_open())
                return false;

        for (const auto& p : mp)
                ofs << p.second << endl;

        bool ret = ofs.good();
        ofs.close();
        return ret;
}

bool people::read(const string& fnam)
{
        mp.clear();
        ifstream ifs(fnam);

        if (!ifs.is_open())
                return false;

        person per;

        while (ifs >> per)
                mp.insert(pair<string, person> (per.getid(), per));

        bool ret = ifs.eof();
        ifs.close();
        return ret;
}

void people::display() const
{
        for (const auto& p : mp)
                p.second.display();
}

void main()
{
        people pep;

        while (1) {
                int choice;

                cout << "0: Exit: " << endl;
                cout << "1: Add: " << endl;
                cout << "2: Display: " << endl;
                cout << "3: Read: " << endl;
                cout << "4. Write: " << endl;
                cin >> choice;

                switch (choice)        {
                        case 0:
                                exit(0);
                                break;

                        case 1:
                                {
                                        string id, nam, age, addr;
                                        cout << "Enter id: ";
                                        cin >> id;

                                        cout << "Enter name: ";
                                        cin >> nam;

                                        cout << "Enter age: ";
                                        cin >> age;

                                        cout << "Enter address: ";
                                        cin >> addr;

                                        if (!pep.insert(person(id, nam, age, addr)))
                                                cout << "Already exists" << endl;
                                }
                                break;

                        case 2:
                                pep.display();
                                break;

                        case 3:
                                if (!pep.read(filname))
                                        cout << "Problem reading file" << endl;

                                break;

                        case 4:
                                if (!pep.write(filname))
                                        cout << "Problem writing file" << endl;

                                break;

                        default:
                                cout << "Invalid option" << endl;
                                break;
                }
        }
}

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PS Don't be tempted to submit this for the assignment as the teacher should spot this!

Much as i like to use that code it won't be accepted in turbo c++ as it doesn't recognize String and i know this isn't the right way of doing c++
but the compiler they are making us use is quite old and have to do it with the unethical way of using c++.
But is there a way of doing bubble sorting in the unethical way as i have tried this code works where if you enter 5 and then 4 it would organize it
but if i then enter 6 the 6 would come on top basically taking the latest input.

If you fix the read issue (in both places you read from the file) and the temp variable problem (have it as a char array) then it seems to work as expected. Note that the sort ordering is based on char ordering and not numeric ordering. So 123 comes before 2 etc.

Quote:

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the compiler they are making us use is quite old and have to do it with the unethical way of using c++

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That's the problem. You shouldn't be using this compiler! :thumbd: You should be taught using an up-to-date compiler that supports c++14 (current version of c++).

Quote:

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Originally Posted by 2kaud

If you fix the read issue (in both places you read from the file) and the temp variable problem (have it as a char array) then it seems to work as expected. Note that the sort ordering is based on char ordering and not numeric ordering. So 123 comes before 2 etc.

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I see that my reading has a issue where it would display a blank empty line after each record but not sure how to fix that issue and i did have temp as a char array but it wasn't doing much difference
hence the reason i had commented it out.
char* temp;//temp[20];

Quote:

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So 123 comes before 2 etc

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how to fix this issue then when using char

For the read issue, consider using something like

Code:

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        char rd[20];

        while (file.getline(rd, 5, '|'))
        {
                char *f = rd;

                if (*rd == 10)
                        ++f;

                if (*f) {
                        strcpy(p[n].id, f);

                        cout << "p[i] id and i value" << n << p[n].id << endl;
                        //file.getline(p[i].name,15,'|');
                        //file.getline(p[i].age,5,'|');
                        //file.getline(p[i].address,15,'!');
                        //i++;
                        n++;
                }
        }

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For the comparison issue, you need to compare as numbers. Consider

Code:

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if (atoi(p[j].id) > atoi(p[k].id))

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where atoi() converts a number as a string into an integer number.

Quote:

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Originally Posted by 2kaud

For the read issue, consider using something like

Code:

---

        char rd[20];

        while (file.getline(rd, 5, '|'))
        {
                char *f = rd;

                if (*rd == 10)
                        ++f;

                if (*f) {
                        strcpy(p[n].id, f);

                        cout << "p[i] id and i value" << n << p[n].id << endl;
                        //file.getline(p[i].name,15,'|');
                        //file.getline(p[i].age,5,'|');
                        //file.getline(p[i].address,15,'!');
                        //i++;
                        n++;
                }
        }

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For the comparison issue, you need to compare as numbers. Consider

Code:

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if (atoi(p[j].id) > atoi(p[k].id))

---

where atoi() converts a number as a string into an integer number.

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Sorry for the late reply had no internet for one week but tys for the answer it worked perfectly well