【洛谷OJ】【JAVA】P1217 [USACO1.5]回文质数 Prime Palindromes

package 新手村.过程函数与递归;

import java.util.Scanner;

public class P1217 {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int a = in.nextInt();
        int b = in.nextInt();
        for(int i=a;i<=b;i++){
            if(i!=2&&i!=3&&i!=5&&(i%2==0||i%3==0||i%5==0)){
                continue;//可以被整除的不算在内
            }
            if(isPalindrome(i)){
                if(isPrime(i)){
                    System.out.println(i);
                }
            }
        }
    }
    public static boolean isPalindrome(int n){
        int x = n;
        int y = 0;
        boolean ret = false;
        while(x!=0){
            y = y*10+x%10;
            x =  x/10;
        }
        if(y==n){
            ret = true;
        }
        return ret;
    }
    public static boolean isPrime(int n){//这里可以通过偶数回文数（11除外）都肯定不是质数，来化简
        boolean ret = true;
        if(n==1||n==2||n==3){
            ret = true;
        }else{
            for(int i=2;i<=Math.sqrt(n);i++){
                if(n%i==0){
                    ret = false;
                    break;
                }
            }
        }
        return ret;
    }
}