How do I create dynamic arrays in c?

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Hello guys,
I create a program in c and I want to use dynamic pointers. The problem is the following....

I have a txt file that contains only two lines of numbers. In the first line there is only one number that says how big must be the array and how many numbers should hold.
In the second line there are as many numbers as the first line say.
-----------------

C++

Eg. file.txt 
9 
982 82 89418 929 98 419925 98 41280 9841

-------------
As you see the first line says that we want to store 9 numbers and in the second line we have the 9 numbers we should store.

The problem is that the number 9 can be from 1 to 250.000 which I can't create a code to store so many numbers.

How can I store until 250.000 numbers in an dynamic array of pointers. Of course when I'll store the numbers i need a different address for each number so in the next part of my code i could call any number i want. How am I suppose to do that?

I read the following courses, but I couldn't understand how am I suppose to do it.
http://www.programiz.com/c-programming/c-dynamic-memory-allocation[^]

Posted 7-Nov-14 3:31am

GeorgeGkas

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Sergey Alexandrovich Kryukov 7-Nov-14 9:53am

The manual you referenced looks clear enough; there are many others. What is your problem, exactly?
What have you tried so far?
—SA

[no name] 7-Nov-14 10:00am

before i'll post the code...first i have question. Do I need to put the numbers in one column and the variable part will be the rows?

Sergey Alexandrovich Kryukov 7-Nov-14 10:32am

What do you mean by "column"? I see no columns. As I understand, first number of first line specifies the number of numbers in second one. Very good. Read/parse this number, take sizeof your numeric type, multiply them. It gives you the number of bytes to allocate. Then allocate the memory for your array.
—SA

[no name] 7-Nov-14 10:02am

well i tried to to make one column and the variable part to be the rows. So i'll have 1D table. The problem I have is eplained very clearly. I will post my code anyway

[no name] 7-Nov-14 10:08am

If I post my code i need to explaine all of that cause it's a very large program. So i tried to specify my problem.

Sinisa Hajnal 7-Nov-14 10:09am

I did a program that analyzed genome, text file with up to 4GB of data. The arrays resulting from the analysis ran into millions of elements before collapsing into final results and never was there a problem. In production the array was never so large, but I tested for it. So your array could be held in memory without problem.

[no name] 7-Nov-14 10:16am

ok thanks for that. But how can I write the code. I have an example but as I said before the program I write is BIGGGGGGGGGG and I can't explaine all the code there. I want only to solve that part so I can put the code in my program. Can you help me?

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Richard MacCutchan · Accepted Answer · 2014-11-07T04:21:00

Solution 1

Read the first line and convert it to an integer.
Use malloc to create a pointer to an array of integers. The array length is set from the number first read.
Read the remaining fields from the text file one line at a time.
Use strtok to split each line into items.
Convert each item to an integer and store in the next free element of the array.
Repeat until all items have been processed.

The documentation for all functions (malloc, strtok etc.) can be found at http://msdn.microsoft.com/en-us/library/634ca0c2.aspx[^].

Posted 7-Nov-14 4:21am

Richard MacCutchan

Comments

[no name] 7-Nov-14 10:27am

ok but I have only two lines. The second line just hold the numbers. Did you mean that? or you mean that I have many lines of numbers? -so I would need many columns-

Richard MacCutchan 7-Nov-14 10:34am

It does not matter whether the numbers are all in one line or many lines, you still only need a single one dimensional array to hold them.