Completing a function using pointers - c

Question

one of the assignments in my class has this objective:
Complete CapVowels(), which takes a string as a parameter and returns a new string containing the string parameter with the first occurrence of each of the five English vowels (a, e, i, o, and u) capitalized.
Hint: Begin CapVowels() by copying the string parameter to a newly allocated string.
Ex: If the input is:
management
the output is:
Original: management
Modified: mAnagEment
This is the current code I have, and I will highlight the section I'm supposed to complete:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
**// Return a newly allocated copy of original
// with the first occurrence of each vowel capitalized
char* CapVowels(char* original) {
return CapVowels(*original= "A.E,I,O,U");
}**
int main(void) {
char userCaption[50];
char* resultStr;
scanf("%s", userCaption);
resultStr = CapVowels(userCaption);
printf("Original: %s\n", userCaption);
printf("Modified: %s\n", resultStr);
// Always free dynamically allocated memory when no longer needed
free(resultStr);
return 0;
}
The section with the ** meaning it's bolded is the section I'm supposed to complete before the int main(void). I can't figure out how to complete the objective. I get mixed up with pointers and dereferencing and, I tried dereferencing when returning the function so that the value will come out to what it's supposed to. I understand one part of it, but I don't know how you would complete it to output to the required output:
Original: management
Modified: mAnagEment

Answer 1

Hint: Begin CapVowels() by copying the string parameter to a newly allocated string.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// Return a newly allocated copy of original
// with the first occurrence of each vowel capitalized
char* CapVowels(const char* original) {
char* result = strcpy(malloc(strlen(original+1)), original);
char* vowels = "aeiou";
while(*vowels)
{
char* ptr = strchr(result, *vowels);
(ptr)? *ptr = toupper(*ptr) : vowels++;
}
return result;
}
int main(void) {
char userCaption[50];
char* resultStr;
scanf("%s", userCaption);
resultStr = CapVowels(userCaption);
printf("Original: %s\n", userCaption);
printf("Modified: %s\n", resultStr);
// Always free dynamically allocated memory when no longer needed
free(resultStr);
return 0;
}
Output
Success #stdin #stdout 0s 5424KB
Original: management
Modified: mAnAgEmEnt

Answer 2

You can use strlen to get the length of the input, then use malloc to allocate enough space for the result. Then, just loop over the input until the terminating null character ('\0'), incrementally assigning the current character to the result if it is a consonant or the uppercase version if it is a vowel (using the toupper function).
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
char *CapVowels(char *original){
if (!original)
return NULL;
const char *vowels = "aeiou";
size_t len = strlen(original); // get length of input (terminating '\0' not included)
char *result = malloc(len + 1); // allocate memory for new string (note that sizeof(char) is 1)
for (char *dest = result; *original; ++original)
*dest++ = strchr(vowels, *original) // check if current character is in the vowels
? toupper(*original) : *original;
result[len] = '\0';
return result;
}

Answer 3

Here's a version that works even with multiple words in 'original'.
char *CapVowels( const char *original ) {
char *cp, *out = strdup( original );
for( char *vowels = "aeiou"; *vowels; vowels++ ) {
if( ( cp = strchr( out, *vowels ) ) != NULL )
*cp = toupper( *cp );
}
return out;
}
void main( void ) {
char userCaption[50];
gets( userCaption );
char *capped = CapVowels( userCaption );
printf( "Original: %s\n", userCaption );
printf( "Modified: %s\n", capped );
free( capped );
}