C program to capitalize a word inside quotation marks - c

Question

I need to build a function that gets an input and capitalizes only the first letter, doesn't print numbers, capitalizes after a . for a new sentence, and capitalizes all words between a double quotation marks ".
This is what I got until now:
#include <stdio.h>
#define MAX 100
int main()
{
char str[MAX] = { 0 };
int i;
//input string
printf("Enter a string: ");
scanf("%[^\n]s", str); //read string with spaces
//capitalize first character of words
for (i = 0; str[i] != '\0'; i++)
{
//check first character is lowercase alphabet
if (i == 0)
{
if ((str[i] >= 'a' && str[i] <= 'z'))
str[i] = str[i] - 32; //subtract 32 to make it capital
continue; //continue to the loop
}
if (str[i] == '.')//check dot
{
//if dot is found, check next character
++i;
//check next character is lowercase alphabet
if (str[i] >= 'a' && str[i] <= 'z')
{
str[i] = str[i] - 32; //subtract 32 to make it capital
continue; //continue to the loop
}
}
else
{
//all other uppercase characters should be in lowercase
if (str[i] >= 'A' && str[i] <= 'Z')
str[i] = str[i] + 32; //subtract 32 to make it small/lowercase
}
}
printf("Capitalize string is: %s\n", str);
return 0;
}
I cant find a way to remove all numbers from input and convert all lowercase to uppercase inside a " plus code for not printing numbers if user input them.
if I input
I am young. You are young. All of us are young.
"I think we need some help. Please" HELP. NO, NO NO,
I DO NOT
NEED HELP
WHATSOEVER.
"Today’s date is
15/2/2021"...
I am 18 years old, are you 20 years old? Maybe 30 years?
output:
I am young. You are young. All of us are young.
"I THINK WE NEED SOME HELP. PLEASE" help. No, no no,
i do not
need help
whatsoever.
"TODAY’S DATE IS
//"...
I am years old, are you years old? maybe years?

Answer 1

The C standard library provides a set of functions, in ctype.h, that will help you
Of particular interest, would be:
isdigit() - returns true if digit
isalpha() - returns true if alphabet character
isalnum() - returns true if alpha/numeric character
islower() - returns true if lower case character
isupper() - returns true if upper case character
tolower() - converts character to lower case
toupper() - converts character to upper case
So, for example, you could replace the test/modify with:
if ( islower( str[i] ) )
{
str[i] = toupper( str[i] );
}
Pedantically, islower() and toupper() return an unsigned int but that's a separate matter...

Answer 2

You can remove letters from a string if you keep two indices, one for reading and one for writing. The following loop will remove all digits from a string:
int j = 0; // writing index, j <= i
int i; // reading index
for (i = 0; str[i]; i++) {
int c = (unsigned char) str[i];
if (!isdigit(c)) str[j++] = c;
}
str[j] = '\0';
(I've used to character classification functions from <ctype.h> mentioned in Andrew' answer.)
This is safe, because j will always be smaller or equal to i. Don't forget to mark the end of the filtered string with the nullterminator, '\0'. You can combine this filtering with your already existing code for replacing characters.
In your code, you capitalize letters only if they are directly behind a full stop. That's usually not the case, there's a space between full stop and the next word. It's better to establish a context:
shift: capitalize the next letter (beginning or after full stop.)
lock: capitalize all letters (inside quotation marks.)
When you read a letter, decide whether to capitalize it or not depending of these two states.
Putting the filtering and the "shift context§ together:
#include <stdio.h>
#include <ctype.h>
int main(void)
{
char str[] = "one. two. THREE. 4, 5, 6. \"seven\", eight!";
int shift = 1; // Capitalize next letter
int lock = 0; // Capitalize all letters
int j = 0; // writing index, j <= i
int i; // reading index
for (i = 0; str[i]; i++) {
int c = (unsigned char) str[i];
if (isdigit(c)) continue;
if (isalpha(c)) {
if (shift || lock) {
str[j++] = toupper(c);
shift = 0;
} else {
str[j++] = tolower(c);
}
} else {
if (c == '"') lock = !lock;
if (c == '.') shift = 1;
str[j++] = c;
}
}
str[j] = '\0';
puts(str);
printf("(length: %d)\n", j);
return 0;
}

Answer 3

In order to remove some characters, you should use 2 index variables: one for reading and one for writing back to the same array.
If you are allowed to use <ctype.h>, it is a much more portable and efficient way to test character types.
Also do not use scanf() with protection against buffer overflow. It is as bad as using gets(). Given the difficulty in specifying the maximum number of bytes to store into str, you should use fgets() instead of scanf().
Here is a modified version:
#include <ctype.h>
#include <stdio.h>
#define MAX 100
int main() {
char str[MAX];
int i, j;
unsigned char last, inquote;
//input string
printf("Enter a string: ");
if (!fgets(str, sizeof str, stdin)) { //read string with spaces
// empty file
return 1;
}
last = '.'; // force conversion of first character
inquote = 0;
//capitalize first character of words
for (i = j = 0; str[i] != '\0'; i++) {
unsigned char c = str[i];
//discard digits
if (isdigit(c)) {
continue;
}
//handle double quotes:
if (c == '"') {
inquote ^= 1;
}
//upper case letters after . and inside double quotes
if (last == '.' || inquote) {
str[j++] = toupper(c);
} else {
str[j++] = tolower(c);
}
if (!isspace(c) && c != '"') {
// ignore spaces and quotes for the dot rule
last = c;
}
}
str[j] = '\0'; // set the null terminator in case characters were removed
printf("Capitalized string is: %s", str);
return 0;
}