Sorting not working

Hello :)
I am making a simple program to accept the details of 3 students and to print the values as the user wants. So i have 3 main options and the 3rd option is sort. If you select sort the program asks you in which way do you want to sort it. And there are 4 options in sorting and i am trying to use selection sort here but none of the 4 sorts are working :( . Hope someone can help me with this and tell me what i have done wrong.If you didnt really understand my question please feel free to ask me.

 #include<iostream.h>
#include<conio.h>
#include<stdlib.h>
#include<iomanip.h>
void enter();
void list();
void query();
void sort();
void percent();
void maths();
void science();
void cs();
struct student
 {
   char name[20];
   int rno;
   float m1,m2,m3,percent;
  }s[3];
char choice;

void main()
{
  clrscr();
  int ch;

    enter();
    cout<<"\n\n\n\t|||||*****------------------------------------------*****|||||";
    cout<<"\n\n\t\t\t\tMENU";
    cout<<"\n\t\t\t\tþþþþ";
    cout<<"\n\n\n\t\t| 1. View the whole list of students |";
    cout<<"\n\n\t\t| 2. View your result                |";
    cout<<"\n\n\t\t| 3. Sort                            |";
    cout<<"\n\n\t\t| 4. Exit                            |";
    cout<<"\n\n\n\t|||||*****------------------------------------------*****|||||";
    cout<<"\n\n\n\t  Enter your choice [1/2/3/4] : ";
    cin>>ch;
    if(ch==1)
    list();
    if(ch==2)
    query();
    if(ch==3)
    sort();
    if(ch==4)
    exit(0);
    getch();
}
void enter()
{
 for(int i=0;i<3;i++)
 {
  cout<<"\n\n\tEnter the name of student "<<i+1<<"         : ";
  cin>>s[i].name;
  cout<<"\n\tEnter the roll no of student "<<i+1<<"      : ";
  cin>>s[i].rno;
  cout<<"\n\tEnter the mark in Maths             : ";
  cin>>s[i].m1;
  cout<<"\n\tEnter the mark in Science           : ";
  cin>>s[i].m2;
  cout<<"\n\tEnter the mark in Computer Science  : ";
  cin>>s[i].m3;
  s[i].percent=(s[i].m1+s[i].m2+s[i].m3)/3;
 }
}


void list()
{
 cout<<"\n\n\n\n\n\tROLL NO"<<setw(12)<<"NAME"<<setw(13)<<"MATHS"<<setw(12)<<"SCIENCE"<<setw(8)<<"C.S";
 for(int i=0;i<3;i++)
  cout<<"\n\t  "<<s[i].rno<<setw(16)<<s[i].name<<setw(12)<<s[i].m1<<setw(10)<<s[i].m2<<setw(9)<<s[i].m3<<endl;
}
void query()
{
 int rnum;
 cout<<"\n\n\n\tEnter your roll number : ";
 cin>>rnum;
 for(int i=0;i<3;i++)
  if(rnum==s[i].rno)
  {
   cout<<"\n\n\t NAME                      : "<<s[i].name;
   cout<<"\n\t Roll no                   : "<<s[i].rno;
   cout<<"\n\t Marks in Maths            : "<<s[i].m1;
   cout<<"\n\t Marks in Science          : "<<s[i].m2;
   cout<<"\n\t Marks in Computer Science : "<<s[i].m3;
   cout<<"\n\t Total Percentage          : "<<(s[i].m1+s[i].m2+s[i].m3)/3;
  }
}
void sort()
{
 int ch;
 cout<<"\n\n\n\t|||||*****------------------------------------------*****|||||";
 cout<<"\n\n\n\t\t| 1. Sort according to total percentage          |";
 cout<<"\n\n\t\t| 2. Sort according to marks in Maths            |";
 cout<<"\n\n\t\t| 3. Sort according to marks in Science          |";
 cout<<"\n\n\t\t| 4. Sort according to makrs in Computer Science |";
 cout<<"\n\n\n\t|||||*****------------------------------------------*****|||||";
 cout<<"\n\n\n\t\tEnter your choice [1/2/3/4] : ";
 cin>>ch;
 if(ch==1)
 percent();
 if(ch==2)
 maths();
 if(ch==3)
 science();
 if(ch==4)
 cs();
}
void percent()
{
 flaot temp;
 for(int i=0;i<3-1;i++)
  for(int j=i+1;j<3;j++)
   if(s[i].percent>s[j].percent)
   {
     temp=s[i].percent;
     s[i].percent=s[j].percent;
     s[j].percent=temp;
    }

 cout<<"\n\n\n\t|||||*****------------------------------------------*****|||||";
 cout<<"\n\n\n\t\tSorted list according to total percentage";
 cout<<"\n\n\n\n\n\tROLL NO"<<setw(12)<<"NAME"<<setw(13)<<"MATHS"<<setw(12)<<"SCIENCE"<<setw(8)<<"C.S";
 for(i=0;i<3;i++)
  cout<<"\n\t  "<<s[i].rno<<setw(16)<<s[i].name<<setw(12)<<s[i].m1<<setw(10)<<s[i].m2<<setw(9)<<s[i].m3<<endl;
 cout<<"\n\n\n\t|||||*****------------------------------------------*****|||||";
}
void maths()
{
 float temp;
 for(int i=0;i<2;i++)
  for(int j=i+1;j<3;j++)
   if(s[i].m1>s[j].m1)
   {
     temp=s[i].m1;
     s[i].m1=s[j].m1;
     s[j].m1=temp;
    }

 cout<<"\n\n\n\t|||||*****------------------------------------------*****|||||";
 cout<<"\n\n\n\t\tSorted list marks in Maths";
 cout<<"\n\n\n\n\n\tROLL NO"<<setw(12)<<"NAME"<<setw(13)<<"MATHS"<<setw(12)<<"SCIENCE"<<setw(8)<<"C.S";
 for(i=0;i<3;i++)
  cout<<"\n\t  "<<s[i].rno<<setw(16)<<s[i].name<<setw(12)<<s[i].m1<<setw(10)<<s[i].m2<<setw(9)<<s[i].m3<<endl;
 cout<<"\n\n\n\t|||||*****------------------------------------------*****|||||";
}
void science()
{
 float temp;
 for(int i=0;i<3-1;i++)
  for(int j=i+1;j<3;j++)
   if(s[i].m2>s[j].m2)
   {
     temp=s[i].m2;
     s[i].m2=s[j].m2;
     s[j].m2=temp;
    }

 cout<<"\n\n\n\t|||||*****------------------------------------------*****|||||";
 cout<<"\n\n\n\t\tSorted list according to makrs in Science";
 cout<<"\n\n\n\n\n\tROLL NO"<<setw(12)<<"NAME"<<setw(13)<<"MATHS"<<setw(12)<<"SCIENCE"<<setw(8)<<"C.S";
 for(i=0;i<2;i++)
  cout<<"\n\t  "<<s[i].rno<<setw(16)<<s[i].name<<setw(12)<<s[i].m1<<setw(10)<<s[i].m2<<setw(9)<<s[i].m3<<endl;
 cout<<"\n\n\n\t|||||*****------------------------------------------*****|||||";
}
void cs()
{
 float temp;
 for(int i=0;i<3-1;i++)
  for(int j=i+1;j<3;j++)
   if(s[i].m3>s[j].m3)
   {
     temp=s[i].m3;
     s[i].m3=s[j].m3;
     s[j].m3=temp;
    }

 cout<<"\n\n\n\t|||||*****------------------------------------------*****|||||";
 cout<<"\n\n\n\t\tSorted list according to marks in Computer Science";
 cout<<"\n\n\n\n\n\tROLL NO"<<setw(12)<<"NAME"<<setw(13)<<"MATHS"<<setw(12)<<"SCIENCE"<<setw(8)<<"C.S";
 for(i=0;i<3;i++)
  cout<<"\n\t  "<<s[i].rno<<setw(16)<<s[i].name<<setw(12)<<s[i].m1<<setw(10)<<s[i].m2<<setw(9)<<s[i].m3<<endl;
 cout<<"\n\n\n\t|||||*****------------------------------------------*****|||||";
}

Last edited on

naaissus (67)

Line 123, 142 etc. for(i=0... should be for(int i=0....
m1, m2, m3, percent are floats and temp should also be float, not int.

1
2

for(int i=0;i<3-1;i++)
for(int j=i+1;j<3;j++)

Using "magic numbers" is considered bad practice, you should really pass number of students as a parameter to a function... For example, because of them you have one logical error on line 161 - you are printing only two students.

Last edited on

Vishnu Vijay (3)

Ok so i changed all the int temp; to float temp; and i have updated the code. Also i am planing to pass the number of students as a parameter but this is just for testing. Still the sorting doesnt work even after i have changed temp to float. Now, i can't give for(int i=0... at line 123 as i have already declared int i in line 111 so declareing it again would be multiple declarations. Thanks for the help anyway :D

naaissus (67)

No. That i on line 111 has local scope only, i. e. only for that specific for loop.

error C2065: 'i' : undeclared identifier

16 times

Last edited on

Vishnu Vijay (3)

How is it like that for you? I have no problem in running the program with my current code excepting the fact that sorting doesnt work and when i give for(int i=0... in like 123 i get error saying multiple declaration for i.

You can see that in this link here
http://imgur.com/zwGERQC

naaissus (67)

Oh, sorry then.
Different compiler, compiling on almost highest level of warnings :D

Btw...
You need to swap whole structures, not just e. g. m1 fields.
I haven't noticed that first time :)

student temp;
 for(int i=0;i<2;i++)
  for(int j=i+1;j<3;j++)
   if(s[i].m1>s[j].m1)
   {
     temp=s[i];
     s[i]=s[j];
     s[j]=temp;
    }

Etc.

Also line 110 misspelling and 161 should be < 3 instead of < 2.

Last edited on

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