Array form of integer

March 31, 2022

I was trying to convert the array to integer sum=999999999999 (twelve 9) , when i am limiting the array to less than ten 9s it is giving the result but when i am giving the array of more than ten 9s it is giving an unexpected result , please explain it will be really helpful for me

int[] arr={9,9,9,9,9,9,9,9,9,9,9,9};
int p=arr.length-1;
int m;
int num=0;
for (int i = 0; i <= p; i++) {
    m=(int) Math.pow(10, p-i);
    num += arr[i]*m;           // it is executing like: 900+90+9=999
}

>Solution :

this happens because you’re exceeding the Integer.MAX_VALUE.

You can read about it here.

You can use instead of int a long, to store large values,
and if that is not enough for you, you can use – BigInteger

BigInteger num = BigInteger.valueOf(0);
for (int i = 0; i <= p; i++) {
    BigInteger m = BigInteger.valueOf((int) Math.pow(10, p-i));
    BigInteger next =  BigInteger.valueOf(arr[i]).multiply(m));
    num = num.add(BigInteger.valueOf(arr[i]*m));
}