fill an array with Int like a Char; C++, cin object

Question

This is a pretty simple question; first time poster and long time looker.

Here is my binary to decimal converter I wrote:

#include <iostream>
#include <cmath>
using namespace std;
const int MAX = 6;
int conv(int z[MAX], int l[6], int MAX);

int main()
{
    int zelda[MAX];
    const int d = 6;
    int link[d];

    cout << "Enter a binary number: \n";  
    int i = 0;
    while (i < MAX && (cin >> zelda[i]).get())  //input loop
    {
        ++i;
    }   

    cout << conv(zelda, link, MAX);

    cin.get();
    return  0;
}

int conv(int zelda[MAX], int link[6], int MAX)
{   
    int sum = 0;
    for (int t = 0; t < MAX; t++)
    {
        long int h, i;
        for (int h = 5, i = 0; h >= 0; --h, ++i)
            if (zelda[t] == 1)
                link[h] = pow(2.0, i);
            else
                link[h] = 0;
            sum += link[t]; 
    }
    return sum;
}

With the way the input loop is being handled, I have to press enter after each input of a number. I haven't added any error correction yet either (and some of my variables are vague), but would like to enter a binary say 111111 instead of 1 enter, 1 enter, 1 enter, etc to fill the array. I am open to any technique and other suggestions. Maybe input it as a string and convert it to an int?

I will keep researching. Thanks.

Your entire input logic is very obscure. Why don't you simply read *one* string, expected to consist of `1`s and `0`s only, and convert that? — Kerrek SB, Nov 25 '11 at 01:32
Best variable nomenclature, EVAR :) (Had to post this comment :)) — ScarletAmaranth, Nov 25 '11 at 02:04
Thanks fellow coders. I honestly didn't give it much thought -_- — Snerd, Nov 25 '11 at 02:29

score 2 · Answer 1 · edited May 23 '17 at 12:27

2

To read data, see this related question (and replace the file stream by std::cin).

To convert, you can do something simple:

unsigned int convert(const std::string & s)
{
  // maybe check that s.size() <= CHAR_BIT * sizeof(unsigned int)

  unsigned int result = 0;

  for (std::string::const_reverse_iterator rit = s.rbegin(), rend = s.rend(); rit != rend; ++rit)
  {
    result *= 2;

    if (*rit == '1') ++result;

    else if (*rit != '0') { /*error!*/ return -1; }
  }

  return result;
}

edited May 23 '17 at 12:27

Community

1
1

answered Nov 25 '11 at 01:35

Kerrek SB

464,522
92
875
1,084

I will read that link and get another angle on how to tackle this. It appears that entering as a string is the best way. – Snerd Nov 25 '11 at 02:27

felipemaia · Accepted Answer · 2011-11-26T17:10:28.613

1

You could read an int and parse it this way:

int number = 0;

cin >> number;
int i = 0;
while(i < MAX)
{
    if(number > 0)
    {
        zelda[i] = number % 10; // or you can switch to zelda[MAX-(i+1)]
        number = number/10;
    else
    {
        zelda[i] = 0;
    }
    i++;
}

EDIT:
Note that this conversion is in little endian format, meaning that if you type the int '100', zelday will be filled with '001'.

EDIT2:
If you want to get it from a string instead, do this, assuming zelda has the same size of str:

string str ("111000");
int i;
for (i=0; i < str.length(); i++)
{
    zelda[i] = (str[i] - '0');
}

Reason why this works:
The numbers represented in a char list are sequential (int this case ASCII), that is, the number zero is represented as 48, the number one is represented by 49, and so on. So when you subtract the representation of the '0', you get the actual number.

edited Nov 26 '11 at 17:10

answered Nov 25 '11 at 01:34

felipemaia

3,381
1
16
14

I like this method, but I might have to work around the endian format. Definitely some ideas. – Snerd Nov 25 '11 at 02:26
Switch the commented version `zelda[MAX-(i+1)]` instead of `zelda[i]`, and you switch around. – felipemaia Nov 25 '11 at 02:27
This is all great. How do I boost your reputation? I don't know if I can at my low rank. – Snerd Nov 25 '11 at 02:49
Just click the up arrow to upvote the answer and then click the V mark to accept it, all users can cast upvotes and accept answers. – felipemaia Nov 25 '11 at 02:51
Ah I tried that just now, but I need 15 rep. Figuring the inner workings of this forum still. – Snerd Nov 25 '11 at 02:55
I really don't think you need any rep to upvote answers or accept them, but read the faq, it won't do you any harm: http://stackoverflow.com/faq Since you're new, read specially the "How do I ask questions here?" and "Etiquette" sections. – felipemaia Nov 25 '11 at 02:57
Thanks. I did read a bit of it before and now I found that detail I was looking for. – Snerd Nov 25 '11 at 03:02
(str[i] - '0') This segment works well. I just need some clarification on the '0' char value. Subtracting the first value in the array by '0' char somehow works.. – Snerd Nov 26 '11 at 02:28
Yes. I got the logic behind this. This is pretty clever. – Snerd Nov 27 '11 at 23:30
The key is in the arithmetic. The minus FORCES a conversion so that the answer has to be an int. Thus, the int can now go inside the array of int. Beautiful. – Snerd Nov 28 '11 at 01:14

fill an array with Int like a Char; C++, cin object

2 Answers2