realloc

#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

*/