Question

I’m trying to write an octal to decimal conversion app.

The problem is the return value is 1 less than it should be, ex.:

INPUT: 2426 (OCT)

SHOULD RETURN: 1302 (DEC)

RETURNS: 1301 (DEC)

Any ideas what’s wrong? I’m using newest Code::Blocks if someone wants to know.

Here’s my code:

int oct2dec (int number) {
    int system  = 8;
    int length  = IntegerLength(number);
    int power   = length - 1;
    int result  = 0;
    int partial = 0;

    do {
        partial = part_nr(number);
        cout<<"czastka: "<<partial<<endl;
        result = result + (partial * pow(system,power));
        number = number - (partial * pow(10,power));
        power--;

    } while (number>0);
    return result; 
}

part_nr function:

int part_nr(int number) {
    int multipler = 1;
    int result    = 0;
    do {
        int temp=number/multipler;
        if(temp<10) result = temp;
        multipler = multipler*10;
    } while (result == 0);
    return result;
}

IntegerLength function:

int IntegerLength(int value) {
   int divisor = 10;
   int length  = 1;
   while(value >= divisor)
   {
     value = (value - (value % divisor)) / divisor;
     length ++;
   }

   return length;
}

(btw. I’ve translated variables from my native lang to english, so if you see any non-eng variable say so, i’ll correct it)

Answer 1

I have tested your code and it is outputting the value you claim to be expected. The only problem I encountered was with rounding. I changed the pow() function call to powf(), and then I cast the result of that function to integer.

This is the code I tested (VS2010 C++ Project):

#include "stdafx.h"
#include <iostream>
#include <cmath>    
using namespace std;

int part_nr(int number) {
  int multipler = 1;
  int result    = 0;
  do {
    int temp=number/multipler;
    if(temp<10) result = temp;
    multipler = multipler*10;
  } while (result == 0);
  return result;
}


int IntegerLength(int value) {
   int divisor = 10;
   int length  = 1;
   while(value >= divisor)
   {
     value = (value - (value % divisor)) / divisor;
     length++;
   }
   return length;
}

int oct2dec (int number) {
  int system  = 8;
  int length  = IntegerLength(number);
  int power   = length - 1;
  int result  = 0;
  int partial = 0;

  do {
    partial = part_nr(number);
    cout<<"czastka: "<<partial<< endl;
    result = result + (partial * (int)powf(system,power));
    number = number - (partial * (int)powf(10,power));
    power--;

  } while (number>0);
  return result; 
}





int _tmain(int argc, _TCHAR* argv[])
{
  int res = oct2dec(2426);
  cout << "res is " << res << endl;
  getchar();
  return 0;
}