#include <stdio.h>
#include <stdlib.h>
#include <string.h>


int main()
{

    int *arr;
    int *tmpArr;
    unsigned int i;
   
    arr = malloc(10*sizeof arr[0]);
    
    if(!arr)
    {
        printf("memory allocation error.\n");
        return 1;
    }
    
    for(i=0; i<10; ++i)
    {
        arr[i] = i;
        printf("%d ",arr[i]);
    }
 
    printf("\n");
 
    //increase
    
    tmpArr = realloc(arr,12*sizeof arr[0]);
    
    if(!tmpArr)
    {
        printf("memory reallocation error.\n");
        free(arr);
        return 1;
    }    
    
    arr = tmpArr;
    
    arr[10]=10;
    arr[11]=11;
    
    for(i=0; i<12; ++i) printf("%d ",arr[i]);
    
    printf("\n");    
    
    //shrink
    
    tmpArr = realloc(arr,8*sizeof arr[0]);
    
    if(!tmpArr)
    {
        printf("memory reallocation error.\n");
        free(arr);
        return 1;
    }
    
    arr = tmpArr;
    
    for(i=0; i<8; ++i) printf("%d ",arr[i]);
    
    printf("\n");
    
    
    free(arr);
    
    return 0;
}

/*

output:

0 1 2 3 4 5 6 7 8 9 
0 1 2 3 4 5 6 7 8 9 10 11 
0 1 2 3 4 5 6 7 

*/