Algorithms/JavaAlgorithms
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refactor: update FastPower

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Libin Yang 2019-05-10 15:42:08 +08:00 committed by GitHub
parent fbffeb658c
commit 1041b02e6b
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1 changed files with 2 additions and 3 deletions
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src/main/java/com/others/FastPower.java
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@ -1,4 +1,4 @@
package src.main.java.com.Others; package src.main.java.com.others;
import java.math.BigInteger; import java.math.BigInteger;
@ -7,14 +7,13 @@ import java.math.BigInteger;
* FastPower aims to calculate quickly in this circumstances with time complexity O(log k), * FastPower aims to calculate quickly in this circumstances with time complexity O(log k),
* where k is the index. * where k is the index.
* *
* @author DDullahan
*/ */
public class FastPower { public class FastPower {
public static BigInteger calculate(BigInteger n, BigInteger k, BigInteger mod) { public static BigInteger calculate(BigInteger n, BigInteger k, BigInteger mod) {
BigInteger ans = BigInteger.ONE; BigInteger ans = BigInteger.ONE;
while (!k.equals(BigInteger.ZERO)) { while (!k.equals(BigInteger.ZERO)) {
int odd = k.mod(BigInteger.valueOf(2)).compareTo(BigInteger.ZERO); int odd = k.mod(BigInteger.valueOf(2)).compareTo(BigInteger.ZERO);
if(odd > 0){ if (odd > 0) {
ans = ans.multiply(n).mod(mod); ans = ans.multiply(n).mod(mod);
} }
k = k.divide(BigInteger.valueOf(2)); k = k.divide(BigInteger.valueOf(2));