Sorting strings doesn't work properly

Question

I have rjecnik.txt file that looks like this

mate sime, jure
stipica gujo, prvi
ante mirkec
goran maja, majica
avion kuca, brod, seoce
amerika, neka, zemlja, krcma
brodarica, zgrada, zagreb
zagreb split
zadar rijeka
andaluzija azija

I need to order lines alphabetically (not words) and my program produces this result which is not correct:

andaluzija azijamate sime, jure
amerika, neka, zemlja, krcma
brodarica, zgrada, zagreb
ante mirkec
avion kuca, brod, seoce
goran maja, majica
stipica gujo, prvi
zadar rijeka
zagreb split

Press [Enter] to close the terminal ... When I use non ascii character like kuća for kuca or krčma for krcma it produces this result (all wrong)

andaluzija azijamate sime, jure
amerika, neka, zemlja, krŔma
brodarica, zgrada, zagreb
ante mirkec
avion kuŠa, brod, seoce
goran maja, majica
stipica gujo, prvi
zadar rijeka
zagreb split

Press [Enter] to close the terminal ... This is my code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
    int ch, nl = 1, min, lenght1, lenght2, lenght;//ch will hold characters, min is for selection sort, lenght holds value of strlen for determine wthat line is longer
    FILE * fp;// FILE pointer
    char * lines[1000];//that will dynamically hold strings for lines
    char * temp;//for lines swaping
    if((fp = fopen("C:\\Users\\don\\Documents\\NetBeansProjects\\proba2\\dist\\Debug\\MinGW-Windows\\rjecnik.txt", "r")) == NULL)//I had to temporarily put full path to rjecnik.txt
    {
        printf("Can't open file...");
        exit(1);
    }
    while((ch = getc(fp)) != EOF)//count lines
    {
        if(ch == '\n')
            nl++;
    }
    int i, j;
    for (i = 0; i < nl; i++)
        lines[i] = malloc(1000);//create array of string size value of nl
    fseek(fp, 0L, SEEK_SET);//go to start of file
    i = 0;
    j = 0;
    while((ch = getc(fp)) != EOF)//fill arrays of string
    {
        lines[i][j] = ch;
        j++;
        if(ch == '\n')
        {
           j = 0;
           i++;
        }
    }
    for(i = 0; i < nl - 1; i++)//selection sort doesn't work properly
    {
        min = i;//min is i
        for(j = i + 1; j < nl; j++)//for number of lines(nl) times
        {
            lenght1 = strlen(lines[i]);//find what string is longer and lenght is smaller one
            lenght2 = strlen(lines[j]);
            if(lenght1 < lenght2)
                lenght = lenght1;
            else
                lenght = lenght2;
            if(strncmp(lines[i], lines[j], lenght) > 0 )//compare two strings
                 min = j;//if second string is alphabetically smaller min is j
        }
        temp = lines[i];// swapping
        lines[i] = lines[min];
        lines[min] = temp;
    }
    for(i = 0; i < nl; i++ )//printing to console
    {
        lenght1 = strlen(lines[i]);
        for(j = 0; j < lenght1; j++ )
        {
            putchar(lines[i][j]);
        }
    }
    return 0;
}

Now program crashes at the end when I add this code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
    int ch, nl = 1, min, lenght1, lenght2, lenght;//ch will hold characters, min is for selection sort, lenght holds value of strlen for determine wthat line is longer
    FILE * fp;// FILE pointer
    char * lines[1000];//that will dynamically hold strings for lines
    char * temp;//for lines swaping
    if((fp = fopen("C:\\Users\\don\\Documents\\NetBeansProjects\\proba2\\dist\\Debug\\MinGW-Windows\\rjecnik.txt", "r")) == NULL)//I had to temporarily put full path to rjecnik.txt
    {
        printf("Can't open file...");
        exit(1);
    }
    while((ch = getc(fp)) != EOF)//count lines
    {
        if(ch == '\n')
            nl++;
    }
    int i, j;
    for (i = 0; i < nl; i++)
        lines[i] = malloc(1000);//create array of string size value of nl
    fseek(fp, 0L, SEEK_SET);//go to start of file
    i = 0;
    j = 0;
    while((ch = getc(fp)) != EOF)//fill arrays of string
    {
        lines[i][j] = ch;
        j++;
        if(ch == '\n')
        {
           j = 0;
           i++;
        }
    }
    for(i = 0; i < nl - 1; i++)//selection sort doesn't work properly
    {
        min = i;//min is i
        for(j = i + 1; j < nl; j++)//for number of lines(nl) times
        {
            lenght1 = strlen(lines[i]);//find what string is longer and lenght is smaller one
            lenght2 = strlen(lines[j]);
            if(lenght1 < lenght2)
                lenght = lenght1;
            else
                lenght = lenght2;
            if(strncmp(lines[min], lines[j], lenght ) > 0 )//compare two strings
                 min = j;//if second string is alphabetically smaller min is j
        }
        temp = lines[i];// swapping
        lines[i] = lines[min];
        lines[min] = temp;
    }
    for(i = 0; i < nl; i++ )//printing to console
    {
        lenght1 = strlen(lines[i]);
        for(j = 0; j < lenght1; j++ )
        {
            putchar(lines[i][j]);
        }
    }
   for (i = 0; i < 100; i++)//Program crashes here
        free(lines[i]);

    return 0;
}

Tio Pepe · Accepted Answer · 2011-10-29 18:15:11Z

2

1.- You must initialize lines to 0 after malloc so strlen works properly. 2.- Compare lines[j] with lines[min] 3.- Don't forget free lines

answered Oct 29, 2011 at 18:15

Tio Pepe

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3 Comments

gameboy Over a year ago

Wait, when I want to free lines at the end of the program with for (i = 0; i < 100; i++) free(lines[i]); program crashes

Daniel Fischer Over a year ago

You're only allocating for n1 lines, so you should only free those.

gameboy Over a year ago

sorry I now I made mistake thinking about somting else

Daniel Fischer · Accepted Answer · 2011-10-29 18:08:35Z

2

You're always comparing lines[j] to lines[i], but you should be comparing it to lines[min].

answered Oct 29, 2011 at 18:08

Daniel Fischer

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Comments

Dave · Accepted Answer · 2011-10-29 20:00:19Z

1

If this isn't you learning about how to sort and get input, c provides qsort() and fgets(), so you could

 int strsort(const void *a, const void *b)
 {
      char *const*astr=a, *const*bstr=b;
      return strcmp(*astr, *bstr);
 }

 main()
 {
     FILE*f = fopen(...);
     char (*arr)[1000] = malloc(1000*1000);
     int x;
     for(x=0;x<1000 && fgets(1000, arr[x], f);x++)
         arr[x][strlen(arr[x])-2] = '\0'; //strip newlines
     qsort(arr, x, 1, strsort);
     int i;
     for(i=0; i<x; i++)
          printf("%s\n", arr[x]);
 }

It's much clearer what you're doing this way.

edited Oct 29, 2011 at 20:00

answered Oct 29, 2011 at 19:47

Dave

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Comments

wildplasser · Accepted Answer · 2011-10-29 18:15:22Z

0

Minor nitpick:

lenght1 = strlen(lines[i]);
            lenght2 = strlen(lines[j]);
            if(lenght1 < lenght2)
                lenght = lenght1;
            else
                lenght = lenght2;
            if(strncmp(lines[i], lines[j], lenght) > 0 )
 ... ;

You don't need this: strcmp() stops when either of the strings terminates, whichever comes first. In your case, you need to compare one more character (the NUL), like

strncmp( lines[i], lines[j], lenght+1)

, otherwise "apple" and "apples" would compare equal (because only the first five characters would be compared). But the "normal" form:

strcmp(lines[i], lines[j])

does exactly what you want.

answered Oct 29, 2011 at 18:15

wildplasser

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