Feb 1, 2012

K & R C Programs Exercise 5-14.

K and R C, Solution to Exercise 5-14:
K and R C Programs Exercises provides the solution to all the exercises in the C Programming Language (2nd Edition). You can learn and solve K&R C Programs Exercise.
Write a C program to handle a -r flag which indicates sorting in reverse (decreasing) order. But sure that -r works with -n.Read more about C Programming Language .

/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define TRUE 1
#define FALSE 0

#define MAXLINES 5000       
char *lineptr[MAXLINES];

#define MAXLEN 1000        

int reverse = FALSE;

int getline(char s[], int lim)
{
 int c, i;

 for (i = 0; i < lim - 1 && (c = getchar()) != EOF && c != '\n'; i++)
  s[i] = c;
 if (c == '\n') {
  s[i++] = c;
 }
 s[i] = '\0';
 return i;
}


int readlines(char *lineptr[], int maxlines)
{
 int len, nlines;
 char *p, line[MAXLEN];

 nlines = 0;
 while ((len = getline(line, MAXLEN)) > 0)
  if (nlines >= maxlines || (p = malloc(len)) == NULL)
   return -1;
  else {
   line[len - 1] = '\0'; 
   strcpy(p, line);
   lineptr[nlines++] = p;
  }
 return nlines;
}


void writelines(char *lineptr[], int nlines)
{
 int i;

 for (i = 0; i < nlines; i++)
  printf("%s\n", lineptr[i]);
}

int pstrcmp(const void *p1, const void *p2)
{
 char * const *s1 = reverse ? p2 : p1;
 char * const *s2 = reverse ? p1 : p2;

 return strcmp(*s1, *s2);
}

int numcmp(const void *p1, const void *p2)
{
 char * const *s1 = reverse ? p2 : p1;
 char * const *s2 = reverse ? p1 : p2;
 double v1, v2;

 v1 = atof(*s1);
 v2 = atof(*s2);
 if (v1 < v2)
  return -1;
 else if (v1 > v2)                                     
  return 1;      
 else
  return 0;
}

int main(int argc, char *argv[])
{
 int nlines;
 int numeric = FALSE;
 int i;

 for (i = 1; i < argc; i++) {
  if (*argv[i] == '-') {
   switch (*(argv[i] + 1)) {
   case 'n':  numeric = TRUE;  break;
   case 'r':  reverse = TRUE;  break;
   default:
    fprintf(stderr, "invalid switch '%s'\n", argv[i]);
    return EXIT_FAILURE;
   }
  }
 }

 if ((nlines = readlines(lineptr, MAXLINES)) >= 0) {
  qsort(lineptr, nlines, sizeof(*lineptr), numeric ? numcmp : pstrcmp);
  writelines(lineptr, nlines);
  return EXIT_SUCCESS;
 } else {
  fputs("input too big to sort\n", stderr);
  return EXIT_FAILURE;
 }
}


Read more c programs 
C Basic
C Strings
K and R C Programs Exercise
You can easily select the code by double clicking on the code area above.

To get regular updates on new C programs, you can

You can discuss these programs on our Facebook Page. Start a discussion right now,

our page!

Share this program with your Facebook friends now! by liking it


(you can send this program to your friend using this button)

Like to get updates right inside your feed reader? Grab our feed!
To browse more C Programs visit this link