# Need help with BigInteger

Nathan Leniz

Ranch Hand

Posts: 132

posted 8 years ago

Having a bit of a problem working on problem 16 on the project euler site.

Given BigInteger base = BigInteger.valueOf(2); for both examples...

<blockquote>code:

<pre name="code" class="core">

BigInteger total = BigInteger.ZERO;

total = base.pow(1000);

</pre>

</blockquote>

gives different output than

<blockquote>code:

<pre name="code" class="core">

BigInteger total = BigInteger.ZERO;

for (int i = 0; i < 1000; i++)

{

total = total.multiply(base);

}

</pre>

</blockquote>

I'm really at a loss. Perhaps it's late and I'm not thinking clearly, but later methods to sum up the individual digits of total aren't giving me the right answer.

Given BigInteger base = BigInteger.valueOf(2); for both examples...

<blockquote>code:

<pre name="code" class="core">

BigInteger total = BigInteger.ZERO;

total = base.pow(1000);

</pre>

</blockquote>

gives different output than

<blockquote>code:

<pre name="code" class="core">

BigInteger total = BigInteger.ZERO;

for (int i = 0; i < 1000; i++)

{

total = total.multiply(base);

}

</pre>

</blockquote>

I'm really at a loss. Perhaps it's late and I'm not thinking clearly, but later methods to sum up the individual digits of total aren't giving me the right answer.

The very existence of flamethrowers proves that at some time, some where, some place, someone once said to themselves "I'd really like to set those people on fire over there, but I just can't get close enough".

Campbell Ritchie

Sheriff

Posts: 50278

80

Nathan Leniz

Ranch Hand

Posts: 132

posted 8 years ago
The very existence of flamethrowers proves that at some time, some where, some place, someone once said to themselves "I'd really like to set those people on fire over there, but I just can't get close enough".

Sorry, getting late. Rather than using BigInteger.Zero in the second loop, I used BigInteger.valueOf(2).

And I found out what it's doing, the second way is actually taking it to the 1001st power. Still no luck on the answer.

Oh, here is the link. Project Euler problem 16.

And I found out what it's doing, the second way is actually taking it to the 1001st power. Still no luck on the answer.

Oh, here is the link. Project Euler problem 16.

Ulf Dittmer

Rancher

Posts: 42968

73

posted 8 years ago

Just as an aside, I've done a fair number of the Project Euler problems in Java, and I've always considered using the BigInteger class as a bit of cheating. It's more interesting to come up with alternative solutions, IMO. The whole point is to learn about algorithms and math, after all.