project euler 35

Problem 35

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Circular primes

The number, 197, is called a circular prime because all rotations of the digits: 197, 971, and 719, are themselves prime.

There are thirteen such primes below 100: 2, 3, 5, 7, 11, 13, 17, 31, 37, 71, 73, 79, and 97.

How many circular primes are there below one million?

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圆周素数

197被称为圆周素数，因为将它逐位旋转所得到的数：197/971和719都是素数。

小于100的圆周素数有十三个：2、3、5、7、11、13、17、31、37、71、73、79和97。

小于一百万的圆周素数有多少个？

package projecteuler;import java.util.ArrayList;import java.util.BitSet;import java.util.HashSet;import java.util.Iterator;import java.util.List;import java.util.Set;import org.junit.Test;public class Prj35 {/** * The number, 197, is called a circular prime because all rotations of the * digits: 197, 971, and 719, are themselves prime. *  * There are thirteen such primes below 100: 2, 3, 5, 7, 11, 13, 17, 31, 37, * 71, 73, 79, and 97. *  * How many circular primes are there below one million? */@Testpublic void test() {System.out.println(Calculator.calculateList(1000000));// System.out.println(Calculator.calculate(1000000));}public static class Calculator {public static int calculateList(int upLimit) {List<Integer> list = new ArrayList<Integer>();for (int i = 2; i <= upLimit; i++) {if (checkIsPrime(i)) {list.add(i);}}Set<Integer> primeSet = filterPrimes(list);List<Integer> ret = new ArrayList<Integer>();Iterator<Integer> iterator = primeSet.iterator();while (iterator.hasNext()) {int val = iterator.next();if (val < 10) {ret.add(val);continue;}int bit = 1;int tmpVal = val;while (tmpVal >= 10) {bit++;tmpVal /= 10;}boolean filter = false;tmpVal = val;for (int i = 0; i < bit; i++) {tmpVal = (int) (tmpVal % Math.pow(10, bit - 1) * 10 + tmpVal/ Math.pow(10, bit - 1));if (!primeSet.contains(tmpVal)) {filter = true;break;}}if (!filter) {ret.add(val);}}System.out.println(ret);return ret.size();}private static Set<Integer> filterPrimes(List<Integer> primeList) {Set<Integer> set = new HashSet<Integer>();for (Integer val : primeList) {if (val < 10) {set.add(val);continue;}int tmpVal = val;boolean hasZeroTwoFive = false;while (tmpVal >= 10) {tmpVal /= 10;// 103 031 310if (tmpVal % 10 == 0 || tmpVal % 10 == 2|| tmpVal % 10 == 4 || tmpVal % 10 == 6|| tmpVal % 10 == 8 || tmpVal % 10 == 5) {hasZeroTwoFive = true;break;}}if (!hasZeroTwoFive) {set.add(val);continue;}}return set;}private static boolean checkIsPrime(int val) {int num = Math.abs(val);if (num >= 10) {for (int i = 2; i <= Math.sqrt(num); i++) {if (num % i == 0) {return false;}}return true;} else {if (num == 2 || num == 3 || num == 5 || num == 7) {return true;}return false;}}public static int calculate(int upLimit) {BitSet bitMap = new BitSet(upLimit + 1);bitMap.set(0);bitMap.set(1);int startId = 0;while (true) {startId = getNext(startId + 1, upLimit, bitMap);System.out.println(startId);if (startId == -1) {break;}for (int i = startId + 1; i < upLimit; i++) {if (i % startId == 0) {setBit(i, true, bitMap);}}}checkCircular(bitMap, upLimit);int count = 0;int fromId = 0;while (-1 != (fromId = bitMap.nextClearBit(fromId))) {count++;}return count;}private static void checkCircular(BitSet bitMap, int upLimit) {int startId = 0;for (;;) {startId = bitMap.nextClearBit(startId);if (startId < 10) {continue;} else {int val = startId;int bit = 1;int tmpVal = val;boolean hasZeroTwoFive = false;while (tmpVal >= 10) {bit++;tmpVal /= 10;// 103 031 310if (tmpVal % 10 == 2 || tmpVal % 10 == 0|| tmpVal % 10 == 5) {hasZeroTwoFive = true;break;}}if (hasZeroTwoFive) {setBit(startId, true, bitMap);continue;}boolean isCircular = true;for (int i = 0; i < bit; i++) {val = (int) (val % Math.pow(10, bit - 1) * 10 + val/ Math.pow(10, bit - 1));if (bitMap.get(val)) {isCircular = false;break;}}if (!isCircular) {val = startId;for (int i = 0; i < bit; i++) {val = (int) (val % Math.pow(10, bit - 1) * 10 + val/ Math.pow(10, bit - 1));if (val < upLimit) {bitMap.set(val);}}continue;}}}}public static void setBit(int id, boolean isPrime, BitSet bitMap) {bitMap.set(id, isPrime);}public static int getNext(int startId, int upLimit, BitSet bitMap) {return bitMap.nextClearBit(startId);}}}