原题链接在这里：https://leetcode.com/problems/prime-palindrome/
题目：
Find the smallest prime palindrome greater than or equal to N.
Recall that a number is prime if it‘s only divisors are 1 and itself, and it is greater than 1.
For example, 2,3,5,7,11 and 13 are primes.
Recall that a number is a palindrome if it reads the same from left to right as it does from right to left.
For example, 12321 is a palindrome.
Example 1:
Input: 6
Output: 7
Example 2:
Input: 8
Output: 11
Example 3:
Input: 13
Output: 101
Note:
1 <= N <= 10^82 * 10^8.题解：
For palindrome, only odd number length could be prime.
Because all even length could be divided by 11. like 1111 % 11 = 0.
Check all odd length palindrome, if it is prime, return it.
AC Java:
1 class Solution { 2 public int primePalindrome(int N) { 3 if(N >= 8 && N <= 11){ 4 return 11; 5 } 6 7 for(int i = 1; i <= 100000; i++){ 8 String half = "" + i; 9 String can = half + new StringBuilder(half.substring(0, half.length() - 1)).reverse().toString(); 10 11 int canVal = Integer.valueOf(can); 12 if(canVal >= N && isPrime(canVal)){ 13 return canVal; 14 } 15 } 16 17 return -1; 18 } 19 20 private boolean isPrime(int n){ 21 if(n < 2 || n % 2 == 0){ 22 return n == 2; 23 } 24 25 for(int i = 3; i * i <= n; i += 2){ 26 if(n % i == 0){ 27 return false; 28 } 29 } 30 31 return true; 32 } 33 34 }
LeetCode 866. Prime Palindrome
原文：https://www.cnblogs.com/Dylan-Java-NYC/p/12185508.html