99 lines
3.4 KiB
Java
99 lines
3.4 KiB
Java
import java.math.BigInteger;
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import java.util.List;
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public class Brazilian {
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private static final List<Integer> primeList = List.of(
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2, 3, 5, 7, 9, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89,
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97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 169, 173, 179, 181,
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191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 247, 251, 257, 263, 269, 271, 277, 281,
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283, 293, 299, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 377, 379, 383, 389,
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397, 401, 403, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 481, 487, 491,
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499, 503, 509, 521, 523, 533, 541, 547, 557, 559, 563, 569, 571, 577, 587, 593, 599, 601, 607,
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611, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 689, 691, 701, 709, 719,
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727, 733, 739, 743, 751, 757, 761, 767, 769, 773, 787, 793, 797, 809, 811, 821, 823, 827, 829,
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839, 853, 857, 859, 863, 871, 877, 881, 883, 887, 907, 911, 919, 923, 929, 937, 941, 947, 949,
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953, 967, 971, 977, 983, 991, 997
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);
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public static boolean isPrime(int n) {
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if (n < 2) {
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return false;
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}
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for (Integer prime : primeList) {
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if (n == prime) {
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return true;
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}
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if (n % prime == 0) {
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return false;
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}
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if (prime * prime > n) {
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return true;
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}
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}
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BigInteger bi = BigInteger.valueOf(n);
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return bi.isProbablePrime(10);
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}
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private static boolean sameDigits(int n, int b) {
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int f = n % b;
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while ((n /= b) > 0) {
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if (n % b != f) {
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return false;
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}
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}
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return true;
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}
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private static boolean isBrazilian(int n) {
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if (n < 7) return false;
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if (n % 2 == 0) return true;
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for (int b = 2; b < n - 1; ++b) {
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if (sameDigits(n, b)) {
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return true;
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}
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}
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return false;
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}
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public static void main(String[] args) {
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for (String kind : List.of("", "odd ", "prime ")) {
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boolean quiet = false;
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int bigLim = 99_999;
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int limit = 20;
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System.out.printf("First %d %sBrazilian numbers:\n", limit, kind);
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int c = 0;
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int n = 7;
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while (c < bigLim) {
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if (isBrazilian(n)) {
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if (!quiet) System.out.printf("%d ", n);
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if (++c == limit) {
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System.out.println("\n");
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quiet = true;
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}
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}
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if (quiet && !"".equals(kind)) continue;
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switch (kind) {
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case "":
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n++;
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break;
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case "odd ":
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n += 2;
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break;
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case "prime ":
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do {
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n += 2;
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} while (!isPrime(n));
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break;
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default:
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throw new AssertionError("Oops");
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}
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}
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if ("".equals(kind)) {
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System.out.printf("The %dth Brazilian number is: %d\n\n", bigLim + 1, n);
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}
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}
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}
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}
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