ANSI C : Stringy, opposite of concatenation type question.

studiorat · 02-05-2010 02:29PM #1

Ok, the user inputs six numbers 123456.

I need to seperate out this input into 12, 34, and 56. Then decide if this is a valid date and print out the date.

What's a good way to break the six digit input into 3 seperate pices of data?

Thanks?

Anima · 02-05-2010 02:41PM

Is it always going to be 3 sets of 2 digit numbers?

Could do somthing like this...
[PHP]
char user_data[7];
int num1, num2, num3;
int temp;
.....
scanf( &user_data, "%d" );

temp = atoi(user_data);
num1 = temp >> 4;
num2 = (temp >> 2)&0x03;
num3 = temp&0x2C;
[/PHP]

Haven't tested, may or may not work as expected.

studiorat · 02-05-2010 03:05PM

Anima wrote: »

Is it always going to be 3 sets of 2 digit numbers?

Could do somthing like this...
[PHP]
char user_data[7]; // sets character array? why 7 and not 6?
int num1, num2, num3;
int temp;
.....
scanf( &user_data, "%d" );

temp = atoi(user_data); // never seen this before what does "atoi" do?
num1 = temp >> 4;
num2 = (temp >> 2)&0x03; // likewise with &0x03, looks like a memory location to me???
num3 = temp&0x2C;
[/PHP]

Haven't tested, may or may not work as expected.

Yeah it's 3 sets of two digit integers...

Was also wondering why char user_data, and not int user_data...

ok atoi converts the string into integers. can I use something like atoi(2) perhaps, for a two digit integer?

Tillotson · 02-05-2010 03:21PM

Or you could do something like this because a char in the range '0' - '9' can be converted to a number by subtracting '0':

int main() {
        int i;
        char *c = "123456";
        int nums[3];

        for (i = 0; i < 3; i++) {
                nums[i] = (*c - '0') * 10 + (*(c + 1) - '0');
                c += 2;
        }
        // check for valid date here
        return 0;
}

padraig_f · 02-05-2010 03:26PM

Sounds like a homework question, what have you got so far?

studiorat · 02-05-2010 05:30PM

it's a couple of tasks from the begining of the year, just got back to them, not done a jot yet...

Working on DSP stuff at the mo, just thinking about this out loud before I start. Gotta get to it before tuesday...

Herbal Deity · 02-05-2010 06:00PM

For strings:

char* date = "123456"
char day[3], month[3], year[3];
sscanf(date, "%2c%2c%2c", day, month, year); 
day[2] = month[2] = year[2] = '\0';

For ints:

int date = 123456;
int day = date/10000;
int month = date/100 & 0x7F;
int year = date & 0x7F;

studiorat · 03-05-2010 01:14PM

Eh, Voila...

int data;
int day, month, year;

main ()
{
    printf ("Please enter six digits : \n");
    scanf ("%d", &data);
    day = data/10000; 
    month = (data/100)- (day*100); 
    year = (data) - (month*100) - (day *10000);

    printf ("You entered %d" ,data);
    printf ("The Date you entered was %d : %d : %d", day, month, year);
    return 0;
}

Thanks for getting the head goin'
I used numbers, I have trouble thinking in characters and strings.
I'm sure I'll be back with more later...

edit: Yup! The only problem is if there is a single integer it doesn't put a zero infront of the integer. So I get 2 : Feb : 2 instead of 02 : Feb : 02

ANSI C : Stringy, opposite of concatenation type question.

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