Reading an unknown # of ints into array

This is a discussion on Reading an unknown # of ints into array within the C Programming forums, part of the General Programming Boards category; Sorry if this is a really simple solution, but it's been a while since I've had a class in C. ...

  1. #1
    jds
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    Reading an unknown # of ints into array

    Sorry if this is a really simple solution, but it's been a while since I've had a class in C. I came across a question about performing some function (let's say summing) a series of integers input from the command line, but the number of integers is up to the user. How do I read in an indeterminant number of values into an array? I've tried using malloc(argc), but the compiler didn't like it. What am I missing? Thanks for any help.

  2. #2
    and the hat of wrongness Salem's Avatar
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    Rough guess, but you don't need an array to store the integers if all you're going to do is sum them
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  3. #3
    End Of Line Hammer's Avatar
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    There are various ways. Maybe a link list would be a good one for this:
    http://cslibrary.stanford.edu/103/

    Or you could use a dynamically sized array (via malloc) and then realloc it when you run out of space.
    http://www.rt.com/man/realloc.3.html

    Whatever, to answer your question on malloc, this will get you enough space to hold a certain number of ints, and you can access it like an array.
    Code:
    #include <stdlib.h>
    
    int *i;
    i = malloc (sizeof(*i) * NUMBER_REQUIRED);
    When all else fails, read the instructions.
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  4. #4
    Just Lurking Dave_Sinkula's Avatar
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    If all the numbers are on the command line, their representations are already stored, so you could try something similar to this.
    Code:
    #include <stdio.h>
    #include <stdlib.h>
    
    int main(int argc, char **argv)
    {
       if(argc > 1)
       {
          int i, sum = 0;
          for(i = 1; i < argc; ++i)
          {
             sum += atoi(argv[i]);
          }
          printf("sum = %d\n", sum);
       }
       return 0;
    }
    
    /* my output
    C:\Test>test 1 2 3 4
    sum = 10
    
    C:\Test>test 1 2 3
    sum = 6
    
    C:\Test>test 1 2 3 4 5
    sum = 15
    */
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