Sieve of Eratosthenes: Difference between revisions
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<pre> |
<pre> |
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There are 168 primes < 1000 |
There are 168 primes < 1000 |
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2 3 5 7 11 13 17 19 23 29 |
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31 37 41 43 47 53 59 61 67 71 |
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73 79 83 89 97 101 103 107 109 113 |
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127 131 137 139 149 151 157 163 167 173 |
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179 181 191 193 197 199 211 223 227 229 |
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233 239 241 251 257 263 269 271 277 281 |
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283 293 307 311 313 317 331 337 347 349 |
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353 359 367 373 379 383 389 397 401 409 |
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419 421 431 433 439 443 449 457 461 463 |
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467 479 487 491 499 503 509 521 523 541 |
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547 557 563 569 571 577 587 593 599 601 |
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607 613 617 619 631 641 643 647 653 659 |
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661 673 677 683 691 701 709 719 727 733 |
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739 743 751 757 761 769 773 787 797 809 |
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811 821 823 827 829 839 853 857 859 863 |
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877 881 883 887 907 911 919 929 937 941 |
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947 953 967 971 977 983 991 997 |
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</pre> |
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===Optimized version=== |
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<lang Zig> |
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const stdout = @import("std").io.getStdOut().writer(); |
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const lim = 1000; |
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const n = lim - 2; |
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var primes: [n]?usize = undefined; |
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pub fn main() anyerror!void { |
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var i: usize = 0; |
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var m: usize = 0; |
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while (i < n) : (i += 1) { |
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primes[i] = i + 2; |
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} |
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i = 0; |
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while (i < n) : (i += 1) { |
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if (primes[i]) |prime| { |
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m += 1; |
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try stdout.print("{:5}", .{prime}); |
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if (m % 10 == 0) try stdout.print("\n", .{}); |
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var j: usize = i + prime; |
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while (j < n) : (j += prime) { |
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primes[j] = null; |
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} |
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} |
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} |
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try stdout.print("\n", .{}); |
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} |
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</lang> |
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{{Out}} |
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<pre> |
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$ zig run sieve.zig |
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2 3 5 7 11 13 17 19 23 29 |
2 3 5 7 11 13 17 19 23 29 |
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31 37 41 43 47 53 59 61 67 71 |
31 37 41 43 47 53 59 61 67 71 |