#include <stdio.h>

/* The C library has a built in function for finding the 
** length of a string (strlen()). This is declared in
** string.h. We could also have used the function
** presented elsewhere in this tutorial.
*/
#include <string.h>

/*
** There are a number of ways of solving this problem
** - a couple are presented below
*/

void reverse_string_and_print(char string[]) {
    int i, len;
    char c;
    len = strlen(string);
    /* We iterate from the first character to the middle.
    ** We swap each character with the the one at the 
    ** other end (note last char is at posn len-1).
    ** If len is odd, the middle position will have 
    ** nothing done to it (which is what we want).
    */
    for(i=0; i < len/2; i++) {
	c = string[i];
	string[i] = string[len-1-i];
	string[len-1-i] = c;
    }
    printf("%s\n", string);
}

/*
** In the following function we don't actually reverse the
** string, we just use a for loop to iterate over each 
** character in the string starting from the end and 
** working our way back to the beginning
*/
void print_string_in_reverse(char string[]) 
{
    int i;
    for(i=strlen(string)-1; i >= 0; i--) {
	printf("%c", string[i]);
    }
    printf("\n");
}

/*
** This function removes the trailing newline from a
** string (if present). We check (a) that the
** string is not empty and (b) if the last
** character (at position length-1) is a newline. If
** so, we turn it into a null character.
*/
void remove_trailing_newline(char string[]) 
{
    int len;
    len = strlen(string);
    if(len > 0 && string[len-1] == '\n') {
	string [len-1] = '\0';
    }
}

int main() 
{
    char string1[80];

    /* Prompt user and get string */
    printf("Enter string: ");
    fgets(string1, 80, stdin);
    remove_trailing_newline(string1);
    printf("String in reverse:\n");
    reverse_string_and_print(string1);
    printf("Reversed again...:\n");
    print_string_in_reverse(string1);

    return 0;
}

/* Remember that when you pass an array to a function it is NOT passed
** by value, i.e. any changes to the array are reflected in the original
** version also. (This is not the case for "scalar" variables, e.g.
** integers and characters).
*/