c strings

K & R C Programs Exercise 7-9.

Posted on by Sandeepa Nadahalli
K and R C, Solution to Exercise 7-9:
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 Functions like isupper() can be implemented to save space or to save time. Explore both possibilities. Read more about C Programming Language .
isupper: return 1 (true) if c is an upper case letter
Normal C function: 
int  isupper(char c)
{
if (c >= 'A' && c <= 'Z')
 return 1;
else
 return 0;
}

This simple code tests the character is upper or lower , If the character within the range of ASCII upper case letters it returns 1, otherwise 0.
To save space or to save time using the macros is the best possibility
C Code: 

#define isupper(c)  ((c) > = 'A' && (c) <= 'Z') ? 1:0

Macro version of isupper is more efficient because, there is no overhead of the function call and it uses more space because the macro is expanded in line every time it is invoked.

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K & R C Programs Exercise 6-2.

Posted on by Sandeepa Nadahalli
K and R C, Solution to Exercise 6-2:
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 that reads a C program and prints in alphabetical order each group of variable names that are identical in the first 6 characters, but different somewhere thereafter. Don’t count words within strings and comments. Make 6 a parameter that can be from the command line. Read more about C Programming Language .
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#include<stdio.h>
#include<ctype.h>
#include<string.h>
#include<stdlib.h>

struct tnode {
 char *word;
 int match;
 struct tnode *left;
 struct tnode *right;
};
#define MAXWORD
#define YES 0
#define NO 0

struct tnode *addtreex(struct tnode *, char *,int, int);
void treexprint(struct tnode *);
int getword(char *,int);


main(int argc, char argv[])
{
 struct tnode  *root;
 char word[MAXWORD];
 int found = NO;
 int num;

 num = (--argc && (*++argv)[0] == '-') ? atoi(argv[0] +1) : 6;
 root = NULL;
 while(getword(word, MAXWORD) != EOF) {
  if(isalpha(word[0]) && strlen(word) >= num)
   root = addtreex(root, word, num, &found);
  found = NO;
 }
 treexprint(root);
 return 0;
}
struct tnode *talloc(void);
int compare(char *,struct tnode *, int, int *);
//addtreex: add a node with w, at or below p
struct tnode *addtreex(struct tnode *p, char *w,int num, int *found)
{
 int cond;
 if(p == NULL) {
  p = talloc();
  p->word = strdup(w);
  p->match = *found;
  p->left = p->right = NULL;
 }
 else if((cond = compare(w,p,num,found)) < 0)
  p->left = addtreex(p->left, w, num, found);
 else if(cond > 0)
  p->right = addtreex(p->right, w, num, found);
 return p;
}

//compare:compare words and update p->match
int compare(char *s,struct tnode *p, int num, int *found)
{
 int i;
 char *t = p->word;
 for(i = 0; *s == *t;i++,s++,t++)
  if(*s == '