Added FastPower #731
Merged
Added FastPower #731
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Added FastPower
havanagrawal
reviewed
May 2, 2019
There was a problem hiding this comment.
This looks like the same functionality as modPow, so the tests should use this as the "expected" value.
| public class FastPowerTest { | ||
|
|
||
| @Test | ||
| public void test() { |
There was a problem hiding this comment.
This should have assert* statements, not printlns.
havanagrawal
reviewed
May 2, 2019
| BigInteger ans = BigInteger.ONE; | ||
| while (!k.equals(BigInteger.ZERO)) { | ||
| int odd = k.mod(new BigInteger("2")).compareTo(BigInteger.ZERO); | ||
| if(odd == 1){ |
There was a problem hiding this comment.
The result of compareTo should only be compared with 0, there is no guarantee that it will be 1, only that it may be negative, 0 or positive.
havanagrawal
reviewed
May 2, 2019
| if(odd == 1){ | ||
| ans = ans.multiply(n).mod(mod); | ||
| } | ||
| k = k.divide(new BigInteger("2")); |
There was a problem hiding this comment.
Instead of using new BigInteger("2") in a loop, we could declare it as a constant outside:
public static final BigInteger TWO = new BigInteger("2");|
Thanks for your review @havanagrawal , I have fixed these problems. |
yanglbme
approved these changes
May 10, 2019
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Added FastPower
We may calculate power with loops, but what if the index is too large ?
FastPower aims to calculate quickly in this circumstances with time complexity O(log k), where k is the index.