K and R C, Solution to Exercise 3-3:
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.
C Program to expand short hand notations like a-z in the string s1 into the equivalent complete list abc—xyz in s2. Allowed for letters of either case and digits, and be prepared to handle cases like a-b-c and a-z0-9 and -a-z. Arranged that a leading or trailing – is taken literally. Read more about C Programming Language .

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#include 
#include 

void expand(char * s1, char * s2);

int main(void) {
 char *s[] = { "a-z-", "z-a-", "-1-6-",
   "a-ee-a", "a-R-L", "1-9-1",
   "5-5", NULL };
 char result[100];
 int i = 0;

 while ( s[i] ) {

  expand(result, s[i]);
  printf("Unexpanded: %sn", s[i]);
  printf("Expanded  : %sn", result);
  ++i;
 }

 return 0;
}



//expand: expand short hand notations in s1 into string s2 
void expand(char * s1, char * s2) {
 static char upper_alph[27] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
 static char lower_alph[27] = "abcdefghijklmnopqrstuvwxyz";
 static char digits[11]     = "0123456789";

 char * start, * end, * p;
 int i = 0;
 int j = 0;


 /*  Loop through characters in s2  */

 while ( s2[i] ) {
  switch( s2[i] ) {
  case '-':
   if ( i == 0 || s2[i+1] == '