Parsing only physical numbers to an array in C

Question

1.00/5 (1 vote)

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can I make an array in Cto hold only positive numbers greater than zero? Like the unsigned type of int, but in array.

I have the following code to make that check when I parsing the elements into the array but I think that this check it 1) slow done the processing, 2) is a wrong method to do the check.

C

[EDIT] Added code from comment
int count = 10;  // Can be 0 - 10
int* children = (int*)malloc(count * sizeof(int));

for (i = 0; i < count; ++i) 
{
    children[i] = atoi(lines[i + 1]);
		
    if (children[i] <= 0)
        return(0);
}

Posted 2-Dec-14 7:21am

GeorgeGkas

Updated 2-Dec-14 8:17am

George Jonsson

v2

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Sergey Alexandrovich Kryukov 2-Dec-14 13:42pm

Please, what is that beast, "physical number"?
—SA

PIEBALDconsult 2-Dec-14 13:49pm

I expect he means "counting number".

[no name] 2-Dec-14 14:04pm

numbers from 0 to ~ (infinite)

Sergey Alexandrovich Kryukov 2-Dec-14 19:51pm

I would say, their not less chemical than physical... :-)
—SA

George Jonsson 2-Dec-14 13:43pm

How did you declare your array?
E.g. unsigned int children[n];

[no name] 2-Dec-14 14:07pm

children = (int*)malloc(count * sizeof(int));

where count is 0-10 ,

George Jonsson 2-Dec-14 14:19pm

With a max count of 10, the speed will be enough for sure.
use unsigned int instead of int for 'children'.
Not really clear exactly what it is you want to do, though.

[no name] 2-Dec-14 14:23pm

I want only to pass numbers greater than 0 in the array else return 0 if a number 0 or less is parseed inside it!

PIEBALDconsult 2-Dec-14 13:44pm

Seems OK to me. If you think that's too slow, then your standards are too high.

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OriginalGriff · Accepted Answer · 2014-12-02T08:11:00

Solution 1

Checking is always worth it: it saves a heck of a lot of grief later on!

The code isn't bad at all - it could possibly use disposal of the multiple-array-access code, but the compiler will likely optimise that anyway.
You could try

C#

for (i = 0; i < count; ++i) {
    if ((children[i] = atoi(lines[i + 1])) <= 0 )
        return(0);
    }

Which might be slightly more efficient, but less readable.

Posted 2-Dec-14 8:11am

OriginalGriff

Comments

[no name] 2-Dec-14 14:43pm

ok so we have the if statement first and we the check on time the elements? Hmmmmm what if we have an array of 2.000.000 ? Is worth to change my code or not?

OriginalGriff 2-Dec-14 15:01pm

For a loop that big, it may be worth some optimisation, but it depends on how likely it is that you will have errors!
If they aren't likely at all, then probably what you have is going to be pretty much optimal, but it's worth doing some timing tests with the release version (so it gets full optimisations) to see if my minor change is worth while - it's worth losing readability to save significant time over a large loop. But not for a loop that runs one in a blue moon and only processes a couple of dozen iterations!