Thread: how to find coomon data in 3 files without rewind..

after the pointed comment
i dont know from what file the smallest belongs to
i dont know in what two files i got the equality
so i could write it somewhere and go the the next line of the "smallest" file
??

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define false 0
#define true 1

char* equal(char*f1,char*f2,char*f3);
  char* smallest(char*f1,char*f2,char*f3);
int main()
{

	FILE *file1,*file2,*file3;
	
	char f1[20];
	char f2[20];
	char f3[20];
	char* small;
    char* equall;	 
	file1=fopen("c:\\1.txt","r");
	file2=fopen("c:\\2.txt","r");
	file3=fopen("c:\\3.txt","r");
	fscanf(file1,"%9s",f1);
	fscanf(file2,"%9s",f2);
	fscanf(file3,"%9s",f3);
	 small=smallest(f1,f2,f3);
	 equall=equal(f1,f2,f3); //how to continue after this point
	                                      
	fclose(file1);
	fclose(file2);
	fclose(file3);
	return 0;
}

char* smallest(char*f1,char*f2,char*f3)
{

	 char* pLowest = f1;
     if(strcmp(pLowest, f2) > 0)
      pLowest = f2;
      if(strcmp(pLowest, f3) > 0)
       pLowest = f3;
      return pLowest;
}

  char* equal(char*f1,char*f2,char*f3)
  {
     if(strcmp(f1,f3)==0)
	 {
       return f1;
	 }
     if(strcmp(f2,f3)==0)
	 {
       return f2;
	 }
	  return NULL;
  }

how to return the file in this function
how to know what file is the smallest string
??

Code:

char* smallest_file(char*f1,char*f2,char*f3,FILE* file1,FILE* file2,FILE* file3)
{

	 char* pLowest = f1;
     if(strcmp(pLowest, f2) > 0)
      pLowest = f2;
      if(strcmp(pLowest, f3) > 0)
       pLowest = f3;
      return pLowest;
}

is there any shorter way then

Code:

char* smallest_file(char*f1,char*f2,char*f3,FILE* file1,FILE* file2,FILE* file3)
{

	 char* pLowest = f1;
     if(strcmp(pLowest, f2) > 0)
      pLowest = f2;
      if(strcmp(pLowest, f3) > 0)
       pLowest = f3;
	  if(strcmp(f1,pLowest)==0)
	  {
		  return file1;
	  }
      if(strcmp(f2,pLowest)==0)
	  {
		  return file2;
	  } 
	  if(strcmp(f3,pLowest)==0)
	  {
		  return file3;
	  }

}

you say to write a function that updates the lowest string(s) by reading from the relevant file.
but i have to know from what file the lowest string came from.

so i cant understand how i can manage doing what you told me
without building such function?

you say
build some how that you could know which file to update each time

but its too abstract
what sub operations i need to build?

ok here is the comparing part

Code:

char* smallest(char*f1,char*f2,char*f3,FILE* file1,FILE* file2,FILE* file3)
{

	 char* pLowest = f1;
     if(strcmp(pLowest, f2) > 0)
      pLowest = f2;
      if(strcmp(pLowest, f3) > 0)
       pLowest = f3;
      return pLowest;
}

here is the scanf part

Code:

      fscanf(file1,"%9s",f1);
	fscanf(file2,"%9s",f2);
	fscanf(file3,"%9s",f3);

for what reason i need to use
"a few if-statements"

ok i tried to write it
but how to know which string is the smallest and which file it belongs to
without writing the previous function that i showed
??

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define false 0
#define true 1

char* equal(char*f1,char*f2,char*f3);
  char* smallest(char*f1,char*f2,char*f3);
int main()
{

	FILE *file1,*file2,*file3;
	
	char f1[20];
	char f2[20];
	char f3[20];
	char* small;
    char* equall;	 
	file1=fopen("c:\\1.txt","r");
	file2=fopen("c:\\2.txt","r");
	file3=fopen("c:\\3.txt","r");

	while(fgetc(f1)!=EOF)||(fgetc(f2)!=EOF)||(fgetc(f1)!=EOF))
	{
	   fscanf(file1,"%9s",f1);
	   fscanf(file2,"%9s",f2);
	   fscanf(file3,"%9s",f3);
	   small=smallest(f1,f2,f3);

	   equall=equal(f1,f2,f3);
	} 
	fclose(file1);
	fclose(file2);
	fclose(file3);
	return 0;
}

char* smallest(char*f1,char*f2,char*f3,FILE* file1,FILE* file2,FILE* file3)
{

	 char* pLowest = f1;
     if(strcmp(pLowest, f2) > 0)
      pLowest = f2;
      if(strcmp(pLowest, f3) > 0)
       pLowest = f3;
      return pLowest;
}

   char* equal(char*f1,char*f2,char*f3)
  {
     if(strcmp(f1,f3)==0)
	 {
       return f1;
	 }
     if(strcmp(f2,f3)==0)
	 {
       return f2;
	 }
	  return NULL;
  }

how to continue??

how to combine those parts

How about using a dynamically allocated array of structs whose elements are: SSN, current file number and a count. SSNs whose count equals 3 are present in all of the files. Just my 2c.