Rev 38 | Show entire file | Regard whitespace | Details | Blame | Last modification | View Log | RSS feed
| Rev 38 | Rev 39 | ||
|---|---|---|---|
| Line 354... | Line 354... | ||
| 354 | // return num.pow(2).toString().endsWith(num.toString()); |
354 | // return num.pow(2).toString().endsWith(num.toString()); |
| 355 | 355 | ||
| 356 | // n² === n (mod 10^m) <===> n²%10^m == n%10^m == n |
356 | // n² === n (mod 10^m) <===> n²%10^m == n%10^m == n |
| 357 | 357 | ||
| 358 | BigInteger m_pow = BigInteger.TEN.pow(m); |
358 | BigInteger m_pow = BigInteger.TEN.pow(m); |
| - | 359 | ||
| 359 | return num.pow(2).mod(m_pow).equals(num); |
360 | //return num.pow(2).mod(m_pow).equals(num); |
| - | 361 | ||
| - | 362 | return num.modPow(BigInteger.valueOf(2), m_pow).equals(num); |
|
| 360 | } |
363 | } |
| 361 | 364 | ||
| 362 | protected static boolean isImmortable(BigInteger num) { |
365 | protected static boolean isImmortable(BigInteger num) { |
| 363 | int m = num.toString().length(); |
366 | int m = num.toString().length(); |
| 364 | return isImmortable(num, m); |
367 | return isImmortable(num, m); |