Question

how to transform strings tho holes

Answer 1

What is a hole? Do you mean (whole) an integral number? What language are we talking about?

In C, you can use atoi().

int i = atoi("123");
printf("i =  %d\n", i);

In Python you can convert string to integer via the constructor of an int:

string = "123"
number = int(string)

In C# various conversion options exist, such as int.TryParse() or Convert.ToInt32().

Java has also various methods. Check this out: https://sentry.io/answers/how-do-i-convert-a-string-to-an-int-in-java/

Comments

You can use std: :stoi (string to integer) to find that too. This one's better because it throws you an invalid_argument if an error occurs, which you can catch and output an error message.
(#include <string>)

Answer 2

#include <stdio.h>
#include <string.h>

void transformString(char str[], char hole) {
    for (int i = 0; str[i] != '\0'; i++) {
        if (str[i] != ' ') { // Replace characters that are not spaces
            str[i] = hole;   // Replace with the specified "hole" character
        }
    }
}

int main() {
    char str[100];
    char hole;

    printf("Enter a string: ");
    fgets(str, sizeof(str), stdin);

    printf("Enter the character to represent holes: ");
    scanf(" %c", &hole); // Note the space before %c to consume any preceding whitespace

    transformString(str, hole);

    printf("Transformed string: %s\n", str);

    return 0;
}