欧拉工程第49题：Prime permutations

题目链接：https://projecteuler.net/problem=49

等间距的三个四位数的质数，并且这四个质数包含同样的数字，求第二个满足条件的数

暴力

Java代码：

package projecteuler41to50;import java.util.Date;
import java.util.Set;
import java.util.TreeSet;class level49{void solve0(){int[] primes=new int[1229];primes[0]=2;int j=1;for(int i=3;j<1229;i+=2)if(isPrime(i)){primes[j++]=i;
// System.out.println(primes[j-1]);}for(int i=0;i<primes.length-1;i++){for(int k=i+1;k<primes.length;k++){if(primes[i]>1000 && sameDigits(primes[i],primes[k])){int diff=primes[k]-primes[i];int lastprime=primes[k]+diff;if(sameDigits(primes[k],lastprime) && isPrime(lastprime) && lastprime<10000){System.out.println(primes[i]+" "+primes[k]+" "+lastprime+" "+diff);}}}}}boolean sameDigits(int num1,int num2){String str1=String.valueOf(num1);String str2=String.valueOf(num2);Set<String> set1=new TreeSet<String>();Set<String> set2=new TreeSet<String>();for(int i=0;i<str1.length();i++){set1.add(str1.substring(i, i+1));}for(int i=0;i<str2.length();i++){set2.add(str2.substring(i, i+1));}if(set1.size()==set2.size())return set1.equals(set2);return false;}boolean isPrime(int num){if(num==2 || num==3 ||num==5||num==7||num==11|| num==13) return true;if(num<2||num%2==0 ||num%3==0) return false;for(int i=3;i<=Math.sqrt(num);++i)if(num%i==0) return false;return true;}
}
public class Problem49 {
    public static void main(String[] args){Date beginTime=new Date();new level49().solve0();Date endTime=new Date();long Time=endTime.getTime()-beginTime.getTime();System.out.println("Time:"+Time/1000+"s"+Time%1000+"ms");}}

结果：

1487 4817 8147 3330
2969 6299 9629 3330
Time:0s904ms