您的位置 首页 Java

第六章第二十六题(回文素数)(Palindromic prime) - 编程练习题答案

**6.26(回文素数)回文素数是指一个数同时为素数和回文数。例如:131是一个素数,同时也是一个回文素数。数学313和757也是如此。编写程序,显示前100个回文素数。每行显示10个数,数字中间用一个空格隔开。如下所示:

2 3 5 7 11 101 131 151 181 191

313 353 373 383 727 757 787 797 919 929

**6.26(Palindromic prime) A palindromic prime is a prime number and also palindromic. For example, 131 is a prime and also a palindromic prime, as are 313 and 757. Write a program that displays the first 120 palindromic prime numbers. Display 10 numbers per line, separated by exactly one space, as follows:

2 3 5 7 11 101 131 151 181 191

313 353 373 383 727 757 787 797 919 929

下面是参考答案代码:

public class Ans6_26_page202 {
    public static void main(String[] args) {
        isPrime(100,10);
    }
    public static void isPrime(int n, int line) {
        int count = 0; // Count the number of prime numbers
        int number = 2; // A number to be tested for primeness

        System.out.println("The first "+n+" numbers are \n");

        // Repeatedly find prime numbers
        while (count < n) {
            // Assume the number is prime
            boolean isPrime = true; // Is the current number prime?

            // Test if number is prime
            for (int divisor = 2; divisor <= number / 2; divisor++) {
                if (number % divisor == 0) { // If true, number is not prime
                    isPrime = false; // Set isPrime to false
                    break; // Exit the for loop
                }
            }

            // Test if number is palindrome
            boolean isPalindrome = true;
            String strNumber = number+"";
            int low = 0;
            int high = strNumber.length() - 1;
            while (low < high) {
                if (strNumber.charAt(low) != strNumber.charAt(high)) {
                    isPalindrome = false;
                    break;
                }
                low++;
                high--;
            }

            // Print the prime number and increase the count
            if (isPrime && isPalindrome) {
                count++; // Increase the count

                if (count % line == 0) {
                    // Print the number and advance to the new line
                    System.out.println(number);
                }
                else
                    System.out.print(number + " ");
            }

            // Check if the next number is prime
            number++;
        }
    }
}

适用Java语言程序设计与数据结构(基础篇)(原书第11版)Java语言程序设计(基础篇)(原书第10/11版)

未注明转载的文章均为原创,并采用 CC BY-NC-SA 4.0 授权协议,转载请注明来源:https://cn.fankuiba.com/344.html

作者: 博主

发表评论

电子邮件地址不会被公开。 必填项已用*标注

返回顶部