Sort numbers (underscore) - c

Question

I am trying to fix my last problem and still, I cannot figure out how to solve it. My task was to write a program which sort numbers, but: our tutor gives us some extra points for program dealing with numbers like: 000054667 (in fact 54667) and 345_845 (in fact 345845). The first problem is already solved but I have no idea how to handle with the second one. Hence, my question is: do you have any tips/clue, which might help me? I am also sending my code:
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#define NUMBER_CHUNK 13
char* getNumber(FILE* fp)
{
int length, c;
int current=0;
char *number;
number=(char*)malloc(sizeof(char)*NUMBER_CHUNK);
if(!number)
{
printf("Error while alocating memory!\n");
return NULL;
}
length=NUMBER_CHUNK;
while(!isspace(c=fgetc(fp)) && !feof(fp))
{
if(isdigit(c))
{
number[current]=c;
current++;
if(current>=length)
{
length+=NUMBER_CHUNK;
if((number=((char*)realloc(number,sizeof(char*)*length)))==NULL)
{
free(number);
return NULL;
}
}
}
else
{
return NULL;
}
}
number[current]='\0';
return number;
}
int compare( const void *str1, const void *str2)
{
int value;
char* curr1;
char* curr2;
curr1=*(char**)str1;
curr2=*(char**)str2;
while(*curr1=='0') curr1++;
while(*curr2=='0') curr2++;
if(strlen(curr1) < strlen(curr2)) return -1;
if(strlen(curr1) > strlen(curr2)) return 1;
value=strcmp(curr1, curr2);
return value;
}
int main(int argc, char** argv)
{
FILE* fp;
char** tab;
int i=0;
int lines=0;
int length=10;
if(argc!=2)
{
printf("Incorrent syntax! Use ./name_of_program input_file\n");
return 1;
}
if(!(fp=fopen(argv[1],"r")))
{
printf("Could not open the file! Please try again!\n");
return 2;
}
tab = (char**)malloc(length*(sizeof(char*)));
if(!tab)
{
printf("Could not allocate memory! Terminating...\n");
free(tab);
return 3;
}
while(!feof(fp))
{
tab[i]=getNumber(fp);
if(i>=length)
{
length+=10;
if((tab=((char**)realloc(tab,sizeof(char*)*length)))==NULL)
{
free(tab);
return 5;
}
}
if(tab[i]==NULL)
{
printf("Incorrect character in the infile! Terminating\n");
free(tab);
return 4;
}
if(*tab[i]=='\0')
{
free(tab[i]);
i--;
}
i++;
lines++;
lines=i;
}
printf("\nBEFORE\n");
for(i=0;i<lines;i++)
{
printf("%s\n",tab[i]);
}
qsort(tab, lines, sizeof(char*), &compare);
printf("\nAFTER\n");
for(i=0;i<lines;i++)
{
printf("%s\n",tab[i]);
free(tab[i]);
}
free(tab);
fclose(fp);
return 0;
}
Thank you for any help ;)

Answer 1

Change string accumulation and your compare routine.
String accumulation:
if(isdigit(c) || (c == '_'))
Compare. This is a bit lengthy to incorporate ignoring _ for value ratings. But it is not limited to numbers that fit in any int range.
int compare(const void *str1, const void *str2) {
const char* curr1 = *(const char**) str1;
const char* curr2 = *(const char**) str2;
// Remove leading zeros
while ((*curr1 == '0') || (*curr1 == '_'))
curr1++;
while ((*curr2 == '0') || (*curr2 == '_'))
curr2++;
int value = 0;
size_t len1 = 0;
size_t len2 = 0;
while (*curr1 || *curr2) {
while (*curr1 == '_')
curr1++;
while (*curr2 == '_')
curr2++;
// If a difference has not been found yet ...
if (value == 0) {
value = *curr1 - *curr2;
}
if (*curr1) {
curr1++;
len1++;
}
if (*curr2) {
curr2++;
len2++;
}
}
// If significant digits in string1 more than string2 ...
if (len1 != len2) {
return (len1 > len2) ? 1 : -1;
}
return value;
}

Answer 2

Just keep parsing the string until you get an underscore, and with parsing also convert each character into the respective number and keep adding it to a new number according to it's place value (In a nutshell i'm speaking of an algorithm to convert string to numbers). and if you encounter an underscore, just use
continue;

Answer 3

If you want to retain the string representation for your "numbers" but compare them according to their numerical value, don't compare them as strings inside your compare function.
Inside compare parse each arguments (str1 and str2) and convert them to numbers skipping leading zeros and underscores. Once you have two numbers (say num1 and num2) just return num1 - num2.

Answer 4

Instead of storing a bunch of strings, you would be better off converting the numbers to ints by stripping out any non-digit characters and calling atoi on the results. You can store those numbers directly in the array. The compare function then becomes much simpler.

Answer 5

chux THX. You're brilliant! I wish I would be as good as you in programming.
I am sending my whole (fixed, working) source code:
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#define NUMBER_CHUNK 13
char* getNumber(FILE* fp)
{
int length;
int current = 0;
int c;
char *number, *number2;
number = (char*)malloc(sizeof(char)*NUMBER_CHUNK);
if(!number)
{
printf("Error while allocating memory!\n");
return NULL;
}
length = NUMBER_CHUNK;
while(!isspace(c = fgetc(fp)) && !feof(fp))
{
if(isdigit(c) || c == '_')
{
number[current] = c;
current++;
if(current >= length)
{
length+=NUMBER_CHUNK;
number2 = (char*)realloc(number,length*sizeof(char*));
if(number2 == NULL)
{
free(number2);
return NULL;
}
else number2 = number;
}
}
else
{
return NULL;
}
}
number[current] = '\0';
return number;
}
int compare(const void *str1, const void *str2)
{
char* curr1;
char* curr2;
curr1=*(char**)str1;
curr2=*(char**)str2;
while(*curr1=='0' || *curr1=='_') curr1++;
while(*curr2=='0' || *curr2=='_') curr2++;
int value = 0;
size_t len1 = 0;
size_t len2 = 0;
while(*curr1 || *curr2)
{
while(*curr1 == '_')
curr1++;
while(*curr2 == '_')
curr2++;
if(value == 0)
{
value = *curr1 - *curr2;
}
if(*curr1)
{
curr1++;
len1++;
}
if(*curr2)
{
curr2++;
len2++;
}
}
if(len1 != len2)
{
return (len1 > len2) ? 1 : -1;
}
return value;
}
int main(int argc, char** argv)
{
FILE* fp;
char** tab;
int i = 0;
int lines = 0;
int length = 10;
if(argc != 2)
{
printf("Incorrent syntax! Use ./name_of_program input_file\n");
return 1;
}
if(!(fp = fopen(argv[1],"r")))
{
printf("Could not open the file! Please try again!\n");
return 2;
}
tab = (char**)malloc(length*(sizeof(char*)));
if(!tab)
{
printf("Could not allocate memory!\n");
free(tab);
return 3;
}
while(!feof(fp))
{
tab[i] = getNumber(fp);
if(i >= length)
{
length += 10;
tab = (char**)realloc(tab,sizeof(char*));
if(tab == NULL)
{
free(tab);
return 5;
}
}
if(tab[i] == NULL)
{
printf("Incorrect character in the infile! Terminating\n");
free(tab);
return 4;
}
if(*tab[i] == '\0')
{
free(tab[i]);
i--;
}
i++;
lines = i;
}
printf("\nBEFORE\n");
for(i = 0 ; i < lines; i++)
{
printf("%s\n", tab[i]);
}
qsort(tab, lines, sizeof(char*), compare);
printf("\nAFTER\n");
for(i = 0; i < lines; i++)
{
printf("%s\n",tab[i]);
free(tab[i]);
}
printf("\n");
free(tab);
fclose(fp);
return 0;
}