C程序将字符串大写不起作用

Question

So, for an assignment, I had to finish a code meant to capitalize a string.

What I tried was this:

#include <stdio.h>

void capitalize(char *str)
{
    int i = 0;
    if (str[i] >= 97 && str[i] <= 122)
    {
        str[i] = str[i] - 32;
    }
    else
    {
        i++;
    }
}

void strCopy(char *str2, char *str1)
{
    while (*str2)
    {
      *str1 = *str2;
      str2++;
      str1++;
    }
    *str1 = '\0';
}

int main(int argc, char **argv)
{
    char string1[100] = "This is a really long string!";
    char string2[100];
    strCopy(string1,string2);
    capitalize(string2);
    printf("The original string is \"%s\"\n", string1);
    printf("The capitalized string is \"%s\"\n", string2);
}

However, when I tried running the code it returned:

The original string is "This is a really long string!"
The capitalized string is "This is a really long string!"

strcopy does not seem to be the issue, as it copies the string1 correctly to string2 .

I don't understand why capitalize is not working, as it seems like it should be going through letter by letter and changing it to uppercase , if the letter falls within the ascii code for a lowercase letter.

I would greatly appreciate someone helping to point out where the error is.

Thanks in advance!

Answer 1

The problem is that your capitilize function doesn't have a loop. You only ever capitalize the first letter of your string.

You are on the right track but what you are looking for is this:

for (int i = 0; str[i] != '\0'; ++i) { // Here we check for the end condition of a string.
                                       // ie. Has the Null termination been reached?
   if (str[i] >= 'a' && str[i] <= 'z') {
      str[i] = str[i] - ('a' - 'A');
   }
}

Here is a live demo for you to play with!

Answer 2

Your capitalize() function only runs for one character. Try like this

for (int i = 0 ; str[i] != '\0' ; ++i) {
    if (str[i] >= 97 && str[i] <= 122)
        str[i] = str[i] - 32;
}

perform the operation on every character until the '\\0' is found.

Answer 3

Try this:

void capitalize(char *str)
{
    int i = 0;
    while (str[i] != '\0')
    {
      if (str[i] >= 97 && str[i] <= 122) {
          str[i] = str[i] - 32;
      }
      i++;
    }
}

Answer 4

you need to fix capitalize(char *str) to check all characters of the string,not just single character.A use of pointer can save you from including <string.h> to use strlen() function,like the following:

#include <stdio.h>

void capitalize(char *str)
{
    char *p = str;
    while(*p++) {
        if (*p >= 97 && *p <= 122) {
            *p -= 32;
        }
    }
}

void strCopy(char *str2, char *str1)
{
    while (*str2) {
        *str1 = *str2;
        str2++;
        str1++;
    }
    *str1 = '\0';
}

int main(int argc, char **argv)
{
    char string1[100] = "This is a really long string!";
    char string2[100];
    strCopy(string1, string2);
    capitalize(string2);
    printf("The original string is \"%s\"\n", string1);
    printf("The capitalized string is \"%s\"\n", string2);
}