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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. class Ideone
  9. {
  10. 	public static boolean isPalindrome(int x) {
  11.         if (x == 0) return true;
  12.         if (x < 0) return false;
  13.  
  14.         int digitsCount = (int) Math.log10(x);
  15.         return isPalindromeHelper(x, 0, digitsCount);
  16.     }
  17.  
  18.     private static boolean isPalindromeHelper(int x, int leftIndex, int rightIndex) {
  19.         int leftDigit = getDigit(x, leftIndex),
  20.             rightDigit = getDigit(x, rightIndex);
  21.  
  22.         if (leftIndex == rightIndex) {
  23.             return true;
  24.         }
  25.         else if (leftDigit != rightDigit) {
  26.             System.out.println("leftDigit="+leftDigit + ", rightDigit=" + rightDigit);
  27.             return false;
  28.         } else {
  29.             return isPalindromeHelper(x, leftIndex + 1, rightIndex - 1);
  30.         }
  31.     }
  32.  
  33.     private static int getDigit(int x, int idx) {
  34.         int digitsCount = (int) Math.log10(x);
  35.         int divisor = ((int) Math.pow(10, digitsCount - idx));
  36.         if (divisor == 0) return x % 10;
  37.                 System.out.println("divisor=" + divisor+",(x/divisor) %10=" + (x/divisor)%10);
  38.         return (x / divisor) % 10;
  39.     }
  40. 	public static void main (String[] args) throws java.lang.Exception
  41. 	{
  42. 		System.out.println(Ideone.isPalindrome(12321));
  43. 	}
  44. }
Success #stdin #stdout 0.19s 57548KB
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stdin
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Standard input is empty
stdout
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divisor=10000,(x/divisor) %10=1
divisor=1,(x/divisor) %10=1
divisor=1000,(x/divisor) %10=2
divisor=10,(x/divisor) %10=2
divisor=100,(x/divisor) %10=3
divisor=100,(x/divisor) %10=3
true
https://ideone.com/3Anp6t
language:
Java (HotSpot 12)
created:
21 hours ago
visibility:
public

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