CODEWITHSUNDEEP
c
seal
seal

Reputation: 21

decimal to binary conversion using recursive functions

I have an assignment to convert a number from decimal to binary. My problem is that I need to have it printed out directly from the function, instead of returning it back to main. Due to this, my printed out code is in the wrong order. (ex: for 6, my code prints out 011 instead of 110)

This is what I have been using for the function: 

int printBinary(int integer) {
    int remainder;

    if (integer < 1) {
        return 0;
    } else {
        remainder = integer % 2;
        printf("%d", remainder);
        integer = integer / 2;
        printBinary(integer);
        return 0;
    }
}

Does anyone have a suggestion on how I can print it out in reverse, or a different approach entirely?

Upvotes: 2

Views: 702

Answers (3)

Eraklon
Eraklon

Reputation: 4288

Also you could try something like this

#include <stdio.h>
#include <limits.h>

void printBinary(int num) {
  int i;

  // findind the first non 0 binary position from MSB
  for (i = sizeof(int) * CHAR_BIT - 1; i >= 0 && (num & (1 << i)) == 0; i--);

  for (; i >= 0; i--) // start the printing from here, so trailing 0's avoided
    if ((num & (1 << i)) == 0)
      printf("0");
    else
      printf("1");
}

int main() 
{
    printBinary(6);
    return 0;
}

Upvotes: 0

chqrlie
chqrlie

Reputation: 144695

You should just print the digit after the recursive call that prints the higher order bits.

Note also that your function prints nothing for 0, which is probably incorrect.

Here is a simplified version:

int printBinary(int integer) {
    if (integer > 1)
        printBinary(integer / 2);
    printf("%d", integer % 2);
    return 0;
}

Upvotes: 2

3CxEZiVlQ
3CxEZiVlQ

Reputation: 38405

Your function prints binary digits starting from the tail. Just change the order of recursive call and printf.

int printBinary(int integer)  {

    int remainder;
    if (integer < 1)  {
    return 0;
    }
    else  {
        printBinary(integer / 2);
        remainder = integer % 2;
        printf("%d", remainder);
    return 0;
    }
}

It was

printBinary(6);
printf("%d", 0);
printBinary(3);
printf("%d", 1);
printBinary(1);
printf("%d", 1);
printBinary(0);

It is now

printBinary(6);
printBinary(3);
printBinary(1);
printBinary(0);
printf("%d", 1);
printf("%d", 1);
printf("%d", 0);

Upvotes: 1

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