Revert a standard input line in C

Question

I am trying to get the following output if the imput be: hi mom the output sera: eam io

the code I made, trying to train recursion was:

#include <stdio.h>

void reverse(char *arr)
{
    if (*arr != EOF)
        reverse((arr + 1));
    printf("%c", *arr);
}

int main()
{
    char input;

    scanf("%s[^\n]", &input);
    reverse(&input);
    return (0);
}

works for the first word, but returns a strange result after giving a space;

Can anyone explain to me why?

Answer 1

What prevents you from reading the two words that are written is the scanf that’s done as:

%s[^\n]

When it should be:

%[^\n]s

But there are several other details that are not right:

• You have to read a string (%s) to an array of char and not a char simple (a letter).
• The string end test has to be done with \0 or 0 and not EOF.
• You are showing the character on the console, even if it is already the last (the '\0').

Fixing all this your code gets like this:

#include <stdio.h>

void reverse(char *arr)
{
    if (*arr != '\0'){ //testa o fim com '\0'
        reverse(arr + 1); 
        printf("%c", *arr); //só mostra se não for \0
    }
}

int main()
{
    char input[30]; //agora string em vez de char

    scanf("%29[^\n]s", input); //formato correto
    reverse(input); //sem o &
    return 0;
}

Check it out at Ideone