Sort an array of char in C

Question

I have been struggling to write a simple code to sort an array of char in C and been failing miserably. This is what I have so far:

int main()
{
  char line[128];
  char word[128];
  int i=0;
  int j;
  int length;

  while(fgets(line,sizeof line,stdin) != NULL)
  {
    length=0;
    i=0;

    while (line[i]!='\0')
      i++;

    length=i;

    line[i-1]=line[i];

    for (i=0;i<=length;i++)
      word[i]=line[i];

    for (i=length-1; i>=0; i--)
    {
      for (j=0;j<i;j++)
      {
        if (line[j] > line[i])
        {
          char temp;
          temp=line[j];
          line[j]=line[i];
          line[i]=temp;
        }
      }
    }

    printf("%s %s\n",line,word);
  }
  return 0;
}

Original file:

overflow
array
test
string
stack

Output file:

 overflow
 array
 test
 string
 stack

This is giving me rather unexpected results. Where am I going wrong?

Can you define "unexpected results"? It works perfectly for me. — casablanca
– casablanca, Commented Oct 14, 2010 at 3:52
@casablanca: If it works for me, then the problem is somewhere else in my code. Let me look into it — Ayush
– Ayush, Commented Oct 14, 2010 at 3:55
This is a follow-up/duplicate of [ C program to sort characters in a string ](stackoverflow.com/questions/3929547/…). As I said there, the sort is inefficient but correct. The output there also shows it working (though there are other errors). — Matthew Flaschen
– Matthew Flaschen, Commented Oct 14, 2010 at 3:59
@JoshD: I think it removes the newline retrieved by fgets. — casablanca
– casablanca, Commented Oct 14, 2010 at 4:10

casablanca · Accepted Answer · 2010-10-14 04:13:50Z

3

Change:

length = i;

to:

length = i - 1;

and it works.

When you do line[i-1] = line[i]; you are removing the \n (which is placed there by fgets) from the line and effectively reducing the string length by 1. You should take that into account.

With your current code, the length includes the null terminator, which gets sorted to the beginning of the string, hence your result is an empty string.

answered Oct 14, 2010 at 4:13

casablanca

70.9k8 gold badges139 silver badges155 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

ruslik · Accepted Answer · 2010-10-14 04:15:34Z

2

Just as I suspected, by avoiding the CR/LF:

length=i;
line[i-1]=line[i];

you included the '\0' characted in the string to be sorted. It will get in the first place, so you'll have an empty string to print.

answered Oct 14, 2010 at 4:15

ruslik

15k1 gold badge42 silver badges42 bronze badges

Comments

codaddict · Accepted Answer · 2010-10-14 04:15:52Z

1

You are removing the \n from the line by overwriting it with \0 but your length calculation is done before this change.

To fix this, do

line[i-1]=line[i];

before you calculate the length.

Since your length is one more than the actual length, \0 is also taking part as a char to be sorted and since its the smallest of all char, it gets placed at the beginning of the string, effectively making your string empty.

answered Oct 14, 2010 at 4:15

codaddict

457k83 gold badges502 silver badges537 bronze badges

Collectives™ on Stack Overflow

Sort an array of char in C

3 Answers 3

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related