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Mar 12th, 2007

Problem in sorting by name

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I am having a problem in sorting by name. for eg: if given two names Sameer and Sean, I want to print Sameer and not Sean. It needs to check character by character. I have to extend this to a greater no. of names but I need to get the basic right first. Here is the code i have written:

C Syntax (Toggle Plain Text)
 
#include<string.h>
#include<conio.h>
#include<stdio.h>
int main(void)
{
 clrscr();
 int flag,x=0;
 char name1[20],name2[20],name3[20],ch,*ptr,*ptr2;
 gets(name1);
 gets(name2);
 flag=0;
  ch=97;
  for(x=0;x<(strlen(name1)) && x<(strlen(name2)) && flag==0;x++)
  {
   ch=97+x;
   ptr = strrchr(name1,ch);
   ptr2 = strrchr(name2,ch);
   if(ptr==ptr2)
   {
    flag=0;
   }
   if(ptr==0 && ptr2!=0)
   {
    strcpy(name3,name1);
    flag=1;
   }
   if(ptr2==0 && ptr!=0)
   {
    strcpy(name3,name2);
    flag=1;
   }
   if(ptr<ptr2)
   {
    strcpy(name3,name1);
   }
   if(ptr>ptr2)
   {
    strcpy(name3,name2);
   }
  }
 printf(" %s",name3);
 getch();
 return 0;
}
#include<string.h>
#include<conio.h>
#include<stdio.h>
int main(void)
{
 clrscr();
 int flag,x=0;
 char name1[20],name2[20],name3[20],ch,*ptr,*ptr2;
 gets(name1);
 gets(name2);
 flag=0;
  ch=97;
  for(x=0;x<(strlen(name1)) && x<(strlen(name2)) && flag==0;x++)
  {
   ch=97+x;
   ptr = strrchr(name1,ch);
   ptr2 = strrchr(name2,ch);
   if(ptr==ptr2)
   {
    flag=0;
   }
   if(ptr==0 && ptr2!=0)
   {
    strcpy(name3,name1);
    flag=1;
   }
   if(ptr2==0 && ptr!=0)
   {
    strcpy(name3,name2);
    flag=1;
   }
   if(ptr<ptr2)
   {
    strcpy(name3,name1);
   }
   if(ptr>ptr2)
   {
    strcpy(name3,name2);
   }
  }
 printf(" %s",name3);
 getch();
 return 0;
}

Some one pls help me out!

Last edited by ankit_the_hawk; Mar 12th, 2007 at 4:09 am.

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ankit_the_hawk

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Mar 12th, 2007

Re: Problem in sorting by name

It is not good practice to use strlen in a for loop, especially for loops that must loop many times because strlen iterates through the array of characters one-by-one every time called (i.e. every loop) and takes up a lot of processor time. You could get the strlen then just used the variables.

Good luck, LamaBot

Last edited by Lazaro Claiborn; Mar 12th, 2007 at 4:35 am.

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Mar 12th, 2007

Re: Problem in sorting by name

Click to Expand / Collapse Quote originally posted by Lazaro Claiborn ...

It is not good practice to use strlen in a for loop, especially for loops that must loop many times because strlen iterates through the array of characters one-by-one every time called (i.e. every loop) and takes up a lot of processor time. You could get the strlen then just used the variables.

Good luck, LamaBot

Ya rite. thnx. I will keep that in mind. Still waiting for the solution though!

ankit_the_hawk

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Mar 12th, 2007

Re: Problem in sorting by name

Click to Expand / Collapse Quote originally posted by ankit_the_hawk ...

C Syntax (Toggle Plain Text)
  for(x=0;x<(strlen(name1)) && x<(strlen(name2)) && flag==0;x++)
  {
   ch=97+x;
   ptr = strrchr(name1,ch);
   ptr2 = strrchr(name2,ch);
for(x=0;x<(strlen(name1)) && x<(strlen(name2)) && flag==0;x++) { ch=97+x; ptr = strrchr(name1,ch); ptr2 = strrchr(name2,ch);

What happens if a string doesn't contain a character for ascii 97 to 97+strlen in its name? If strchr encountered a character not located in the string, it'll return NULL. What if the strlen of name1 is larger than name2? You'd be checking 8 char's for name1 and matching character 97+8 to name2 which could contain only 5 char's and even then, not all the ascii char's were checked since you're checking from 97+strlen of a given name, for instance. You could do something like this:

c Syntax (Toggle Plain Text)
string name1, name2;
int len = name1.length(), len2 = name2.length(), x;
for (x=0;x<len-1 || x<len-1;x++) {
 if (name1[x]>name2[x]) 
  name1.swap(name2)
}
string name1, name2;
int len = name1.length(), len2 = name2.length(), x;
for (x=0;x<len-1 || x<len-1;x++) {
 if (name1[x]>name2[x]) 
  name1.swap(name2)
}

The above uses strings and not character arrays, but it is an example. Last, you might want to convert the string to check on lower case characters in my example, because character at x might be larger in name1 if it is lowercase but the alpha character still comes before x in name2 which is a capital letter and thus will always be smaller than any of its lower case counter parts.

Good luck, LamaBot

Last edited by Lazaro Claiborn; Mar 12th, 2007 at 5:10 am.

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Mar 12th, 2007

Re: Problem in sorting by name

I think you you use Turbo C, so string class wont work with your compiler, because Turbo C++ is old compiler and supports AT&T C++ not ANSI C++.

And yes you should also not use gets() and puts() functions. Also clrscr() and getch() are also not standardised.

Here's the code. I have removed some unnecessary variables.

c Syntax (Toggle Plain Text)
#include<string.h>
#include<conio.h>
#include<stdio.h>
 
 
int main(void)
{
 clrscr();
 
 char name1[20],name2[20];
 int *ptr;
 gets(name1);
 gets(name2);
 
 int s1 = strlen(name1);
 int s2 = strlen(name2);
 
(s1<=s2)?ptr=&s1:ptr=&s2;
 
 int x, flag=0;
 
 for( x=0;x<*ptr;x++)
 {
 
     int ch = (int)name1[x], _ch = (int)name2[x];  // takes one character
 
     if(ch<97)        {  ch+= 32; }         // converts to lowercase
     else if(_ch<97)  { _ch+= 32; }
 
    // if bot characters are not equal, loop is terminated.
    // flag is -1 for name2 and 1 for name2 and 0 if equal
 if(ch!=_ch)                                  
     {
       if(ch>_ch)flag=-1; else flag=1;
       break;
     }
 }
 
 if(flag==1)
     puts(name1); 
else if(flag==-1) 
     puts(name2); 
 
 getch();
 return 0;
}
#include<string.h>
#include<conio.h>
#include<stdio.h>


int main(void)
{
 clrscr();

 char name1[20],name2[20];
 int *ptr;
 gets(name1);
 gets(name2);

 int s1 = strlen(name1);
 int s2 = strlen(name2);

(s1<=s2)?ptr=&s1:ptr=&s2;

 int x, flag=0;

 for( x=0;x<*ptr;x++)
 {

     int ch = (int)name1[x], _ch = (int)name2[x];  // takes one character

     if(ch<97)        {  ch+= 32; }         // converts to lowercase
     else if(_ch<97)  { _ch+= 32; }

    // if bot characters are not equal, loop is terminated.
    // flag is -1 for name2 and 1 for name2 and 0 if equal
 if(ch!=_ch)                                  
     {
       if(ch>_ch)flag=-1; else flag=1;
       break;
     }
 }

 if(flag==1)
     puts(name1); 
else if(flag==-1) 
     puts(name2); 

 getch();
 return 0;
}

Last edited by vishesh; Mar 12th, 2007 at 6:13 am.

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Mar 12th, 2007

Re: Problem in sorting by name

Yeah.... the code I'd posted was an example. I indicated this when I said

Quote ...

...., but it is an example.

Lazaro Claiborn

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Mar 12th, 2007

Re: Problem in sorting by name

strcmp() doesn't interest you...oh well.:rolleyes:

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Mar 12th, 2007

Re: Problem in sorting by name

Ankit, like Iamthwee said, strcmp ( ) coupled with qsort ( ) function should work out to be fine in your case.

~s.o.s~

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Mar 12th, 2007

Re: Problem in sorting by name

Here is a program that might help you: http://www.daniweb.com/code/snippet660.html

Good luck, LamaBot

Lazaro Claiborn

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Mar 12th, 2007

Re: Problem in sorting by name

>Here is a program that might help you
Somehow I kind of doubt that when the code doesn't even compile. :rolleyes:

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