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Adding to an array in C

I have an array with a given size, without using memory allocation, how do I add something to it?

Let's say I run the code expecting something you want to enter, enter "bond"

how to add this to the array? A [10]?

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If the array is declared as

char A[10];

then you can assign it a "link" like this



#include <string.h>

//...

strcpy( A, "bond" );

If you want to add an array with a different string, you can write

#include <string.h>

//...

strcpy( A, "bond" );
strcat( A, " john" );
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You cannot add an array. When you define an array variable, C asks that there is enough contiguous memory. This is all the memory you have ever received. You can change the elements of the array (A [10] = 5), but not the size.

However, you can create data structures that allow you to add. The two most common are linked lists and dynamic arrays. Please note: they are not built into the language. You have to implement them yourself or use a library. Python, Ruby and JavaScript lists and arrays are implemented as dynamic arrays.



LearnCThHardWay has a pretty good tutorial on linked lists, although one of the dynamic arrays is a little crude.

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Hello,

It really depends on what you mean by adding.

...
int tab[5]; // Your tab, with given size
// Fill the tab, however suits you.
// You then realize at some point you needed more room in the array
tab[6] = 5; // You CAN'T do that, obviously. Memory is not allocated.

The problem here can be two:

  • Have you misjudged the size you want? In this case, just make sure that the size you specified is correct, however it may be.
  • Or don't you know how much space you want at the beginning? In this case, you will have to allocate memory yourself! There is no other way to resize a chunk of memory on the fly, so to speak.




    #include <stdio.h>
      

        
        
        
      

      #include <stdlib.h>
      

        
        
        
      

      #include <string.h>
      

        
        
        
      

      #define STR_MAX_SIZE 255
      

        
        
        
      

    //   .  .  
  char * new_string (char * str)   {     char * ret;//  ;     ret = (char *) malloc (sizeof (char) * 255);//      strcpy (ret, str);//    C string.h     return (ret);   } 
  int main()   {     char *  [STR_MAX_SIZE];//      char  [255];//      int  = 0, j = 0;// 
        ( [0]!= 'q')       {         printf ( "!  smth:\n" );         scanf ( "% s", in);          [i] = new_string (in);//     malloc          ++;       }     for (; j < i; j ++)       {         printf ( "Tab [% d]:\t% s\n", j,  [j]);//          ( [J]);// . ,                                                             //      malloc         } 
    return (0);   }


code>
This is the easiest solution I could think of. This is probably not the best, but I just wanted to show you the whole process. I could use the C standard library function strdup(char *str)

to create a new line, and I could implement my own quick list or array.

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The size of the array variable cannot change. The only way to add to an array is using memory allocation. You are looking for a function realloc()

.

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If you want to add a character or string to it;

strcpy(a, "james")
strcpy(a, "bond")
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