Performance Issue while generating random numbers and inserting into an Array with already n numbers

Here is the code that I am using for generating random numbers and inserting them into an array. Say if I want to generate 1000000 random numbers and insert into an array with already MAXSIZE number of elements at a random position generated. the below logic is actually crashing my system due to low heap memory for a very long number.

Here MAXSIZE = 1000000

srand(time(NULL));
for (int i = 0; i<MAXSIZE; i++)
{
    int randomNo = rand() % MAXSIZE;
    randArray[i] = randomNo;
}

//Inserting Random numbers for an Array at a random position
    for (int i = position, j = 0; i < (2 * size); i++, j++)
    {
        bArray[j] = aArray[i];
        aArray[i] = randArray[j];
    }

    for (int i = position + size, j = 0; i < ((2 * size)); i++, j++)
    {
        aArray[i] = bArray[j];
    }

Can someone suggests a better way of writing the code here so that the system doesn't crash for a very large set of numbers and put it in an array.