Newbie? printing an array backwards

[d2rover]

Hello all, newbie here and yes I am trying to do homework. I have spent the last couple days searching the forums trying to learn. I havent been in school in years (lots of years) and I am struggling with some of the concepts. I dont want anyone to do my homework I just want to learn.

I need to code a program that asks the user to input a line of text and then prints the text in reverse. Here is what I have so far. Any suggestions on what I am missing or what I should go read/study would be appreciated. Am I barking up the wrong tree using strlen?

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

int main(void)
{
	char text[500];
	int letters = 0;

	printf("Please enter a line of text.\n");
	gets(text);
	
	letters = strlen(text)-1;
	while (letters <= 0)
	{
		printf("Your reversed text reads:  %s\n", text[letters]);
		--letters;
	
	}
	
	
getchar();
getchar();
return 0;

[Adak]

Don't you want letter >=0 ??

gets() is horribly unsafe! Use

fgets(arrayName, sizeof(arrayName), stdin);

instead. You'll love it.

[Salem]

First, you need to get out of the habit of using gets()
SourceForge.net: Gets - cpwiki

> Am I barking up the wrong tree using strlen?
No, but when has a string length been less than zero?

Here.
> while (letters <= 0)

Also, %s does not print single letters.

[d2rover]

First, you need to get out of the habit of using gets()
SourceForge.net: Gets - cpwiki

> Am I barking up the wrong tree using strlen?
No, but when has a string length been less than zero?

Here.
> while (letters <= 0)

Also, %s does not print single letters.

Thanks guys! Instructions were to use "gets" function. I do understand the the "while" problem, brain fart on that one.

[Elysia]

Complain and point them to the resource. Keep using fgets if they don't fail you. If they still don't change their mind, then you can use gets. But remember never to use it outside school.

[d2rover]

Thank you Elysia (and others), I will bring it up. I did read ahead in the book as to why fgets should be used. We aren't actually to the chapter on gets/fgets function but were told to look it up and use "gets" function.

Program runs but prints only one character on each line preceeded by "Your reversed text reads: ". I assume I have a problem in my "while" loop?

Here is what I so far:

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

int main(void)
{
	char text[500];
	int letters = 0;

	printf("Please enter a line of text.\n");
	gets(text);
	
	letters = strlen(text)-1;
	while (letters >=0)
	{
		printf("Your reversed text reads:  %c\n", text[letters]);
		--letters;
	
	}
		
getchar();
getchar();
return 0;
}

[Elysia]

That's what you told it to do.
The loops reads:

While letters >= 0 do
print "Your reversed text reads: "
print letter at text[letters].
print newline.
decrement letters.
Repeat.

Rework that logic a little and you'll see it will work.

[codecaine_21]

This prints any string you enter under the specified array size and prints it backwards! Very simplistic, if you havent already got it by now.

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

int main()
{
   char str1[20];
   int a;
   printf("Please enter a sentence under 20 characters. ");
   fgets(str1, sizeof(str1), stdin);
   for(a = strlen(str1); a > -1; --a) printf("%c", str1[a]);
   return 0;
}

[Elysia]

Don't spoil the solution. People learn by trying. If you spoil the solution, they won't learn that part.

[codecaine_21]

sorry Elsia, but i felt that a working example would give him a better understanding. Wont happen again

[Elysia]

Working examples are good. But also keep in mind that logic is something that newbies need to learn. It is essential.
So guiding them through it rather than showing a full featured example is usually a better idea.

[codecaine_21]

The best way to learn and gain experience definitely would be to mess with code yourself so i completely understand and respect your seniority to this board and your wishes!

[Babkockdood]

Here's how I would do it.

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

int main() {
    int x;
    char y[500];
    fgets(y, sizeof(y), stdin);
    for (x = (strlen(y) - 2); x >= 0; x--)
        putchar(y[x]);
    putchar('\n');
    return 0;
}

gets is unsafe. I assigned x to the length of y minus two so it doesn't print the newline character.

[Elysia]

...gets is unsafe...

That has been pointed out already.
(Don't you read links or replies?)

[Babkockdood]

That has been pointed out already.
(Don't you read links or replies?)

Yes. Why not remind him once more?