编写一个程序来读取 n 个数字。指定为输入的第一个数字将是 n。接下来，程序应该读取 n 个整数。程序应该检查每个数字是否是素数以及它的反向是否是素数。按升序显示所有这些数字。考虑下面的输入和输出示例：输入：7 11 12 23 19 7 113 101输出：7 11 101 113我的代码public class Prime { public static void main(String[] args) { Scanner sc = new Scanner(System.in); int x = sc.nextInt(); int temp; int[] a = new int [x]; int[] r = new int [x]; int[]c = new int[a.length+r.length]; int[] rev = new int [x]; for(int i=0;i<x;i++){ a[i] = sc.nextInt(); rev[i]=a[i]; } for(int i = 0; i < a.length; i++) { while(rev[i] != 0) { r[i] = r[i] * 10; r[i] = r[i] + rev[i]%10; rev[i] = rev[i]/10; } } for(int i = 0; i < a.length; i++) { boolean isPrime = true; for (int j = 2; j < i; j++) { if((a[i]%j==0) || (r[i]%j==0)) { isPrime = false; break; } } if(isPrime) System.out.println(a[i]); System.out.println(r[i]); } }}在某个地方我被卡住了我不知道如何消除重复的否，最后如何合并数组，并且当我给出输入和 2 时它打印 1 和 2 作为素数
4 回答
叮当猫咪
TA贡献1776条经验 获得超12个赞
您需要使用 TreeSet - 它只包含不同的元素并以排序形式给出结果。您可以参考以下代码-
Set<Integer> set = new TreeSet<>();
for(int i = 0; i < a.length; i++) {
boolean isPrime = true;
if(isPrime(a[i]) && isPrime(r[i]))
set.add(a[i]);
}
Iterator it = set.iterator();
while(it.hasNext())
System.out.print(it.next() + " ");
还创建一个检查素数的函数 -
private static boolean isPrime(int num) {
if(num==1) return false;
for(int i = 2; i <= num/2; ++i)
{
if(num % i == 0)
{
return false;
}
}
return true;
}
阿晨1998
TA贡献2037条经验 获得超6个赞
你可以试试下面的代码。希望对你有帮助
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;
public class PrimeNumberTest {
public static void main(String[] args) {
List<Integer> list = new ArrayList<>(Arrays.asList(7, 11, 12, 23, 19, 7 ,113, 101));
//To remove duplicates
Set<Integer> set = new TreeSet<>(list);
System.out.println(getPrimeNumbers(set).toString().replaceAll(",", "").replace("]", "").replace("[", ""));
}
//Method to get unique ordered set of prime numbers
private static Set<Integer> getPrimeNumbers(Set<Integer> set) {
Set<Integer> resultList=new TreeSet<>();
set.forEach(ele->{
//check for prime
if(isPrime(ele)){
//if prime number check for reverse and if true, add to result
if(isPrime(reverserNumb(ele)))
resultList.add(ele);
}
});
return resultList;
}
private static boolean isPrime(int num){
if(num<2)
return false;
// Check for even numbers
if (num % 2 == 0) {
return num == 2;
}
// Check for odd numbers
for (int i = 3; i*i <= num; i += 2) {
if (num % i == 0) {
return false;
}
}
return true;
}
private static int reverserNumb(int num) {
return Integer.valueOf(new StringBuilder(String.valueOf(num)).reverse().toString());
}
}
呼啦一阵风
TA贡献1802条经验 获得超6个赞
试试这个代码是否有效，希望它有帮助
代码：
import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;
public class PrimeNumbers {
static ArrayList<Integer> prime = new ArrayList<>();
public static void main(String[] args) {
Scanner user_input = new Scanner(System.in);
System.out.print("Enter Number of Integers: ");
int number_count = user_input.nextInt();
int[] numbers = new int[number_count];
for (int i = 0; i < numbers.length; i++) {
System.out.print("Enter Integer: ");
numbers[i] = user_input.nextInt();
}
System.out.print("Values Entered: ");
for (int i = 0; i < numbers.length; i++) {
System.out.print(numbers[i] + " ");
checkPrime(numbers[i],false); //false don't reverse
checkPrime(numbers[i],true); //true reverse value to check if it is also prime
}
System.out.print("\nList of prime numbers: ");
Collections.sort(prime);
for(int n : prime){
System.out.print(n + " ");
}
if(prime.isEmpty()){
System.out.print("no prime numbers on list\n");
}
}
//check for duplicates
static void insertValueToPrime(int n){
for(int p : prime){
if(n == p){
return;
}
}
prime.add(n);
}
static void checkPrime(int n,boolean isReverse) {
int i, m = 0, flag = 0,realn = n;
if(isReverse){
n = reverseNumber(n);
}
m = n / 2;
if (n == 0 || n == 1) {
//no a prime number
} else {
for (i = 2; i <= m; i++) {
if (n % i == 0) {
// not a prime number
flag = 1;
break;
}
}
if (flag == 0) {
insertValueToPrime(realn);
}
}
}
static int reverseNumber(int n){
String reverse = "",str=""+n;
for(int i = str.length() - 1; i >= 0; i--)
{
reverse = reverse + str.charAt(i);
}
return Integer.parseInt(reverse);
}
}
繁星点点滴滴
TA贡献1803条经验 获得超3个赞
这是使用 √n 方法进行质数测试的代码
static boolean isPrime(int n){
//corner case
if (n <= 1) return false;
if (n <= 3) return true;
//middle 5 number
if (n % 2 == 0 || n % 3 == 0) return false;
for (int i = 5; i * i <= n; i = i + 6)
if (n % i == 0 || n % (i + 2) == 0)
return false;
return true;
}
使用可set用于删除重复元素
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