Replacing letter on string C language - c

Question

i'm practicing strings now and what i try to do in this program is print something like: hello world into HellO WorlD as an output.
My code is the following one:
#include <stdio.h>
#include <string.h>
void convertir(char cadena[200]){
int length = strlen(cadena);
int i;
printf("%c", cadena[0]-32); // Prints letter in caps
for(i=1;i<length-1;i++){
if(cadena[i] == ' '){ // Search if there is space
printf("%c", cadena[i-1]-32);
i=i+1; // Adds vaule on i with accumulator to make caps the letter after the space
printf(" %c", cadena[i]-32); // prints letter in caps after space
} else {
printf("%c", cadena[i]); // prints everything in the string
}
}
printf("%c", cadena[length-1]-32);
}
int main(int argc, char const *argv[]) {
char cadena[200];
printf("Introduce un texto: ");
gets(cadena);
convertir(cadena);
return 0;
}
What the code compiled returns me after typing hello world is: HelloO WorlD, i'm trying to replace that o in HelloO but i'm getting confused...
Any help is appreciated.
Thank you.

Answer 1

I made the following changes to your for loop and it appears to work as you expect it to:
for(i=1;i<length-1;i++)
{
if(cadena[i + 1] == ' ') /*** Look If Next Character Is A Space ***/
{
printf("%c", cadena[i]-32); /*** Print Current Character In Uppercase ***/
i=i+1; // Adds vaule on i with accumulator to make caps the letter after the space
printf(" %c", cadena[i + 1]-32); /*** Print Character After Space In Caps ***/
i=i+1; // Adds vaule on i with accumulator to make caps the letter after the space
}
else
{
printf("%c", cadena[i]); // prints everything in the string
}
}
Output:
$ ./main.exe
Introduce un texto: hello world
HellO WorlD
Moving forward, there are several things you should do to make your program more robust:
Don't assume there aren't leading spaces (or whitespace)
Don't assume each character is lowercase
Don't assume each character is a letter
Don't assume there is only one space (or whitespace) between words

Answer 2

Any help is appreciated.
Use isalpha() to detect if a char is part of a word.
Use toupper() to convert to an uppercase character.
Use unsigned char for isalpha(), toupper() to avoid UB with negative char values.
Employ a boolean to keep track if a beginning of a word is possible.
#include <ctpye.h>
#include <stdbool.h>
void convertir(const char *cadena) {
const unsigned char *s = (const unsigned char *) cadena;
bool potential_start_of_word = true;
while (*s) {
// If next character is not an alpha or we area at the start of a word ...
if (!isapha(s[1]) || potential_start_of_word) {
printf("%c", toupper(*s));
} else {
printf("%c", *s);
}
potential_start_of_word = !isapha(*s);
s++;
}
}
No need for strlen(cadena)

Answer 3

You can use ctype.h's toupper() function or provide your own implementation. Something like this:
int toupper(int c) {
return (c-32);
}
And then use it like this:
#include <stdio.h>
#include <string.h>
#include <ctype.h>
void convertir(char cadena[200]){
int length = strlen(cadena);
int i;
cadena[0] = toupper(cadena[0]);
cadena[length-1] = toupper(cadena[length-1]);
for(i=0; i<length; i++){
if(cadena[i] == ' '){ // Search if there is space
cadena[i-1] = toupper(cadena[i-1]);
if (i+1 < length) cadena[i+1] = toupper(cadena[i+1]);
}
}
printf("%s\n", cadena);
}
int main(int argc, char *argv[]) {
char cadena[200];
printf("Introduce un texto: ");
gets(cadena);
convertir(cadena);
return 0;
}