Controlling tab position for correct indentation in output

Question

How can I control the tab position in order to properly indent a piece of code given as input?

I use a counter for the brackets to set the proper amount of indentation (e.g. if the first { is in position 1 then the next should be in position 9).

Here is my code:

#include <stdio.h>
#include <stdlib.h>

main() {
  int ch;
  ch = getchar();
  int lbcounter = 0; // Left curly bracket counter
  int rbcounter = 0; // Right curly bracket counter
  while (ch != EOF) {
    if (ch != ';' && ch != '{' && ch!= '}') {
      putchar(ch);
    }
    if (ch == ';') {
      putchar(ch);
      putchar('\n');
    }
    if (ch == '{') {
      putchar('\n');
      if(lbcounter == 0) {
        putchar('\n');
        lbcounter++;
        putchar(ch);
        putchar('\n');
      } else {
        putchar('\t');
        lbcounter++;
        putchar(ch);
        putchar('\n');  
      }
    }
    if (ch == '}') {
      putchar('\n');
      if(rbcounter == 0) {
        putchar('\t');
        rbcounter++;
        putchar(ch);
        putchar('\n');
      } else {
        putchar('\n');
        rbcounter++;
        putchar(ch);
        putchar('\n');
      }
    }
    ch = getchar();
  }
}

For example, for the following input:

int main(void){{{{{{{;;(void)((((0))));;return 0;}}}}}}}

we expect the following output:

int main(void)
{
    {
        {
            {
                {
                    {
                        {
                            ;
                            ;
                            (void)((((0))));
                            ;
                            return 0;
                        }
                    }
                }
            }
        }
    }
}

but the actual output is:

int main(void)

{

    {

    {

    {

    {

    {

    {
;
    ;
    (void)((((0))));
    ;
    return 0;

    }


}


}


}


}


}


}

To sum up: each time a left curly bracket is read from the input, I want to increase the indentation by one \t — unless it is the first one, in which case I just want to insert a newline.

When the first right curly bracket is read, I want it to match the position of the last left bracket. Each time a new right bracket is read, the indentation should then decrease by one \t.

Answer 1

I have reviewed your code and you have got fundamental programming logic problems I think you should practice programming such algorithms more in order to promote your programming skill and your algorithmic thinking ability.

I have written a code that will do the job for you But you have to always remember that programming is sometimes a very long process of coding and trying different inputs and then analysing the outputs.

And in some cases debugging a written code is more important than the coding itself.

Here is the code:

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int ch;
    ch = getchar();
    int prevch=ch;
    int lbcounter=0; /*Left curly bracket counter*/
    int rbcounter=0; /*Right curly bracket counter*/
    while (ch != EOF)
    {
        if (ch != ';' && ch != '{' && ch!= '}')
        {
            if(prevch=='\n')
            for(int i=lbcounter;i>0;i--)
            {
               putchar('\t');
            }
            putchar(ch);
            prevch=ch;
    }
    if (ch == ';')
    {
        if (prevch == ';' || prevch == '{' || prevch== '}'||prevch=='\n')
        for(int i=lbcounter;i>0;i--)
        {
            putchar('\t');
        }
        putchar(ch);
        putchar('\n');
        prevch='\n';
    }
    if (ch == '{')
    {

        if(lbcounter==0)
        {
                putchar('\n');
                lbcounter++;
                putchar(ch);
                putchar('\n');
                prevch='\n';
        }   
        else
        {

            for(int i=lbcounter ;i>0;i--)
            {
                putchar('\t');
            }
            putchar(ch);
            lbcounter++;
            putchar('\n');
            prevch='\n';
        }

    }
    if (ch == '}')
    {

        lbcounter--;
        for(int i=lbcounter;i>0;i--)
        {
            putchar('\t');
        }
        putchar(ch);
        putchar('\n');
        prevch='\n';
    }

    ch=getchar();
}
}

And as the last advise try to understand the code instead of just using it.

The logic for the first if block: You have to take into concern that for characters except ';' , '}' , '{' there should the the same number of tabs before the characters to put the characters in the same indentation level of the block that was created by the last '{' character , and if only the previous character was the '\n' there must be tabs because for a string like 'void' you shouldn't put tabs between two characters.

The logic of the second if block: This if blocks does the same thing as the first if block with two differences First: it puts a new line character after the ';' character and Second : puts the required tab only if the previous character that was put is one of the following ';','}','{','\n' , because in a string like 'void;' the tabs shouldn't be placed before the ';' character.

The logic of the third if block: You know that the a '{' should be followed by a '}' character with the same indentation level so you have saved the indentation level of the last '{' character in the 'lbcounter' so you put the same number of tabs just before the '}' and after each '}' the indentation level decreases by one 'labcounter--'.

Answer 2

The problem is that indentation is not preserved when you insert a newline character. What you need is a variable that stores the current number of tabs.

int tab_qty = 0; // before your while loop
tab_qty++; // after printing a left bracket
tab_qty--; // before printing a right bracket

Then you insert \t N times (where N = tab_qty) at the beginning of lines.

Answer 3

#include <stdio.h>

int main(){
    int ch;
    int bcounter=0; /* bracket counter */
    int topOfLine = 1;

    while((ch=getchar()) != EOF){
        if(ch == '{' || ch == '}'){
            if(!topOfLine)
                putchar('\n');
            topOfLine = 1;
        }
        if(ch == '}'){
            --bcounter;
        }
        if(0 < bcounter && topOfLine){
            int i;
            for(i = 0; i < bcounter; ++i)
                putchar('\t');
        }
        putchar(ch);
        topOfLine = 0;
        if(ch == '{' || ch == ';'){
            putchar('\n');
            topOfLine = 1;
        }
        if(ch == '{'){
            ++bcounter;
        }
    }
}