How do you write a program to delete all the vowels from a sentence assuming the sentence is no more than 80 characters long?

Answer 1

There is no need to assume the length if the sentence is represented by a null-terminated string. The following function will strip out all the vowels in any null-terminated string of any length, returning the number of vowels removed. Note that we don't create a new string, we simply modify the existing one since we know the modified string cannot be any longer than the existing one. If you want to retain the original string, simply make a copy of it before invoking this function.

The p variable is a pointer and will initially refer to the first character of str, which is also a pointer. The cnt variable maintains a count of the vowels we removed. We use the str pointer to advance through the string one character at a time. When str is referring to a vowel we simply advance str to the next character leaving p where it is (effectively ignoring the vowels) and increment cnt. When str refers to a non-vowel, we copy the character from str to p and advance both pointers. When str reaches the null-terminator, we place a null-terminator in p and return the value of cnt.

If any vowels were found there will be cnt characters beyond the new null-terminator. If the original string was a fixed-length array then you cannot remove these extra characters, but for variable length strings you may wish to reallocate, reducing the size of the allocation by cnt characters.

int strip_vowels (char* str)

{ char * p = str;

int cnt = 0;

if (str==NULL) return cnt;

while (*str != '\0') // test for null-terminator

{

switch (*str) // test for vowels

{

case 'a': case 'A':

case 'e': case 'E':

case 'i': case 'I':

case 'o': case 'O':

case 'u': case 'U':

str++; // str refers to a vowel, so ignore and advance to next character

cnt++; // increment the count

break;

default:

*p++ = *str++; // non-vowel -- copy the character and advance both pointers

break;

}

}

*p = '\0'; // ensure the modified string is null-terminated!

return cnt;

}