Thread: reversing the content of array character-wise

I am a newbie and havent read pointers yet. This programme breaks in the function when it is supposed to reverse the characters.e-g "four" --> "ruof"

Herre is what i did.
I created another array of same size to copy the contents of first array and was thinking of for loop going from the length of character to the zero subscript and print those values.

Any help would be appreciated. All i am interested in is what should be the right for loop with appropriate condition to put the characters on screen in reverse.

Code:

#include <stdio.h>
#define MAX_SIZE 10

int string_length_func(char string_data[],char reverse_string[]); //func prorotype

int main(void)
{
	/* Declare a character array to store the string in */
	
	char string_data[MAX_SIZE];
	char reverse_string[MAX_SIZE];

	int length_word;

	/* Ask the user for a string */
	printf("Enter a word: ");
	scanf("%9s", string_data);
	
        length_word = string_length_func(string_data,reverse_string);
	
	return 0;
}

int string_length_func(char string_data[],char reverse_string[])
{
	char reverse_word=5;
	int element_num =0;

for (element_num = 0; 
	(element_num < MAX_SIZE) && !(string_data[element_num] == '\0'); 
	element_num ++)
	{
		reverse_string[element_num] = string_data[element_num];
	}

for( reverse_word = --element_num;(reverse_word <= element_num) && (reverse_word >=0);reverse_word --)

{
	printf("%s\t",reverse_string[element_num]);
}

return (element_num);
}

Why do people overcomplicate things so much?

Code:

for( x = start; fromhere[ x ]; x++ )
    tohere[ x ] = fromhere[ end - x - 1 ];

Oh, and you will need to null terminate your new string. Here's a Christmas present:

Code:

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

void revs( char fromhere[], char tohere[] )
{
    size_t x;
    
    for( x = 0; fromhere[ x ]; x++ )
        tohere[ x ] = fromhere[ strlen( fromhere ) - x - 1 ];
    tohere[ x ] = '\0';
}

int main( void )
{
    char a[BUFSIZ] = "Hello World!";
    char b[BUFSIZ] = {0};
    
    revs( a, b );
    
    puts( a );
    puts( b );
    
    return 0;
}

If you don't like Christmas, too bad, here's a present anyway.



Quzah.

strlen()

what are the other functions?
also, a quick search on google will yield results for explanations of the functions :]

Well you don't have to have strlen in there. All it does is calculate the length of a string. You can make your own. Simply walk through a string character by character, and count until you reach the null. Don't count it.

Code:

size_t mystrlen( char *s )
{
    size_t len = 0; /* size_t is a variable type, unsigned,
                       which is safe to use for array indexing */
    for( len = 0; s[ len ]; len++ ) /* for each letter, stop on null, increment len */
        ; /* don't do anything, just count */

    return len; /* return the length */
}

There are many ways to do it, that's just a simple version to learn by.

Anyway, my code was basically this:

Code:

for each letter in the 'fromhere' string, stopping when we reach the end do:
    take this position, noted by x, of the 'tohere' string, and fill it with
    the character at 'the end' - x - 1

now add a null on to the end of 'tohere'

That is to say, if a string is 10 characters in length, not counting its null, do this:

Code:

tohere[ x ] = fromhere[ 10 - x - 1 ];

Or:

Code:

foo[ 0 ] = bar[ 10 - 0 - 1 ];

Which translates to:

Code:

foo[ 0 ] = bar[ 9 ];

We subtract 1, because array indexing begins at zero, not 1. Naturally you repeat this throughout:

Code:

foo[0] = bar[9];
foo[1] = bar[8];
foo[2] = bar[7];
...
foo[7] = bar[2];
foo[8] = bar[1];
foo[9] = bar[0];

foo[ 10 ] = a null character, to terminate the string

You can do the last part inside the loop if you change your loop conditions slightly. I'll leave that as an exercise to the reader, if you really feel like it.

Quzah.

Originally Posted by willc0de4food

what are the other functions?

Probably puts. The puts function takes a string of characters, and sends it to the standard output device (commonly your screen), including a newline character. Thus, if the string is "foo", it will end up sending "foonewlinecharacter", where newlinecharacter is of course the newline character, and not the actual phrase newlinecharacter.


Quzah.

Reversing a string in place:
http://www.daniweb.com/code/snippet259.html