hdu.1016 Prime Ring Problem_prime ring problem解题public static void main-优快云博客

本文链接：https://blog.youkuaiyun.com/l_vaule/article/details/44918135

本博客探讨了一个算法，用于输入任意整数n，计算并打印从1到n的所有质数序列，并检查特定条件下的质数和是否为质数。

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import java.util.Arrays;
import java.util.Scanner;


public class Main
{
public static void main(String[] args)
{
    int n,count = 0;
    int prime[] = new int[30];;
    Scanner input = new Scanner(System.in);
    
    while (input.hasNextInt())
    {    count++;
        n = input.nextInt();
        Arrays.fill(prime, 0);
        prime[0] = 1;
        System.out.println("Case "+count+":");
        find(n, 1, prime);
        System.out.println();
    }
    
}


private static void find(int n,int cur,int[] prime)
{
    // TODO Auto-generated method stub
    if (cur == n && is_prime(prime[0] + prime[cur-1]))
    {
        for (int i = 0; i < n; i++)
        {
            if (i == 0)
            {
                System.out.print(prime[i]);
            }
            else {
                System.out.print(" "+prime[i]);
            }
        }
        System.out.println();
    }
    else {
        for (int i = 2; i <= n; i++)
        {
            boolean is = true;
            prime[cur] = i;
            for (int j = 0; j < cur; j++)
            {
                if (prime[j] == i)
                {
                    is = false;
                    break;
                }
                
            }
            if (is_prime(prime[cur] + prime[cur - 1]) && is)
            {
                find(n, cur+1, prime);
            }
        }
    }
}


private static boolean is_prime(int n)
{
    // TODO Auto-generated method stub
for (int i = 2; i <= Math.sqrt(n); i++)
{
    if (n % i == 0)
    {
        return  false;
    }
}
return true;
}
}

dfs,不需要剪剪枝。