Converting Ascii to binary in C

问题:

So here is my code

void ascToBinary(int character, int *ones)
{
    if(character == 1)
    {
       printf("1");
       *ones+=1;
       return;
    }
    else
    {
        if((character%2) == 0)
        {
             printf("0");
             character = character/2;
        }
        else
        {
             printf("1");
             character = character/2;
             *ones+=1;

        }
        binaryPrinter(character, ones);
    }
}

Can anyone try to help me out on where something is wrong here. It compiles fine and does some ascii letters correct. If you try an 'e' though it will print out '1010011' instead of the correct binary.

All help appreciated Thanks Guys.

回答1:

You print the results in the wrong order. The correct output is '1100101'. You can flip it like this:

    void ascToBinary(int character, int *ones)
    {
        if(character == 1)
        {
           printf("1");
           *ones+=1;
           return;
        }
        else
        {
            char out;
            if((character%2) == 0)
            {
                 out = '0';
                 character = character/2;
            }
            else
            {
                 out = '1';
                 character = character/2;
                 *ones+=1;

            }
            ascToBinary(character, ones);
            putchar (out);
        }
    }

回答2:

You're printing the bits of the character in reverse, since you start printing with the least significant bit.

Therefore the expected value for your function, when called on e is 1010011 which is exactly what you get.

回答3:

Converting an Integer to binary:

Version 1 - Will print out the binary result

void to_bin(int value)
{
    char base_range[] = "01";

    if (value >= 2) {
        to_bin(value / 2);
    }

    printf("%c", base_range[value % 2]);
}

Version 2 - Will return a string with binary result

void to_bin_str(int value, char *res, int *p)
{
    char base_range[] = "01";

    if (value >= 2) {
        to_bin_str(value / 2, res, p);
    }

    res[(*p)++] = base_range[value % 2];
}

char* convert(int value)
{
    char* result = (char*)malloc(sizeof(char) * 32);
    int i = 0;

    to_bin_str(value, result, &i);
    result[i] = '\0';

    return (result);
}

Version 3 - Will convert to any base from 2 to 16, handles negatives for base 10

void to_base(int value, int base, char *res, int *p)
{
    char base_range[] = "0123456789ABCDEF";

    if (value >= base || value <= -base) {
        to_base(value / base, base, res, p);
    }

    res[(*p)++] = base_range[abs(value % base)];
}

char* convert(int value, int base)
{
    char *result = (char*)malloc(sizeof(char) * 32);
    int i = 0;

    if (base < 2 || base > 16)
        return (NULL);

    if (base == 10 && value < 0)
        result[i++] = '-';

    to_base(value, base, result, &i);
    result[i] = '\0';

    return (result);
}