一個數同時爲素數和迴文數,顯示前100個迴文素數
代碼:
package com.im;
public class Demo626 {
public static void main(String[] args) {
// TODO Auto-generated method stub
// long Num = 1000000000;
int count = 1;
for(int i=2; true; i++){
if(isPrimeNum(i) && isPalindrome(i)){
System.out.printf("%6d",i);
if(count%10 == 0){
System.out.println();
}
if(count == 100){
break;
}
count++;
}
}
}
//判斷是否是素數
public static boolean isPrimeNum(long Num){
for(int i=2; i<=Num/2; i++){
if(Num % i == 0){
return false;
}
}
return true;
//如果Num不存在
}
//判斷是否是迴文數
public static boolean isPalindrome(long Num){
if(Num == reverse(Num)){
return true;
}else{
return false;
}
}
//求出此數的倒置數
public static long reverse(long Num){
long v = 0; //位數上的數字
long m = 0; //倒置數
int count = digitOfNumber(Num);
for(int i=1; i<=count; i++){
v = Num % 10;
m += v*Math.pow(10, count-i);
Num /= 10;
}
return m;
}
//求出此數的位數
public static int digitOfNumber(long Num){
int count = 0; //位數的計數器
while(Num > 0){
Num /= 10;
count++;
}
return count;
}
}