How to convert a string

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I have this code for converting a string from L to R to R to L but I think something is wrong it - given an input I get "smilies" as an output. Why?

C#

#include <stdio.h>
#include <string.h>
#define MAXLINE 100

int main()
{
    char s[MAXLINE];
    int c, i, j;
    printf("Input string: \n");
    for(i = 0; i < MAXLINE - 1 && (c = getchar() != EOF) && c != '\n'; i++)
        s[i] = c;
    if (c == '\n')
    {
        s[i] = c;
        i++;
    }
    s[i] = '\0';
    printf("%s\n", s);
    for(i = 0, j = strlen(s) - 1; i < j; i++, j--)
    {
        c = s[i];
        s[i] = s[j];
        s[j] = c;
    }
    printf("%s\n", s);
    return 0;
}

Posted 23-Apr-15 18:01pm

yngwie123

Updated 23-Apr-15 18:43pm

v4

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Comments

PIEBALDconsult 24-Apr-15 0:18am

"Can it be modified somehow?"
Yes, I'd use an editor.
What seems to be the problem?

Sergey Alexandrovich Kryukov 24-Apr-15 0:20am

"Something is wrong" is not informative at all. You did not even tag what is it? C? C++?
Sorry, the post makes little to no sense.
—SA

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OriginalGriff · Accepted Answer · 2015-04-23T19:19:00

If you run your code in the debugger, and put a breakpoint in the first loop:

C++

s[i] = c;

Then a quick look at your variables will show you the value of "c" is "1" - regardless of the key you press!

And then it's obvious: it's an operator precedence problem.
Because "Not Equals" has a higher priority than "Assignment" this part:

C++

(c = getchar() != EOF)

Is evaluated to mean

If getchar() is not EOF assign "1" to "c", otherwise assign "0" to "c"

Rather than

Assign the value returned by getchar() to "c", and then check if it is an EOF

Just change the brackets from this:

C++

for(i = 0; i < MAXLINE - 1 && (c = getchar() != EOF) && c != '\n'; i++)

To this:

C++

for(i = 0; i < MAXLINE - 1 && (c = getchar()) != EOF && c != '\n'; i++)

And it'll work.