34 lines
982 B
D
34 lines
982 B
D
import std.stdio, std.math, std.string, std.conv, std.algorithm,
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std.range;
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bool isPrime(in int n) pure nothrow {
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if (n <= 1)
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return false;
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foreach (immutable i; 2 .. cast(int)sqrt(real(n)) + 1)
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if (!(n % i))
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return false;
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return true;
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}
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bool isTruncatablePrime(bool left)(in int n) pure {
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immutable s = n.text;
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if (s.canFind('0'))
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return false;
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foreach (immutable i; 0 .. s.length)
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static if (left) {
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if (!s[i .. $].to!int.isPrime)
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return false;
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} else {
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if (!s[0 .. i + 1].to!int.isPrime)
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return false;
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}
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return true;
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}
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void main() {
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enum n = 1_000_000;
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writeln("Largest left-truncatable prime in 2 .. ", n, ": ",
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iota(n, 1, -1).filter!(isTruncatablePrime!true).front);
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writeln("Largest right-truncatable prime in 2 .. ", n, ": ",
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iota(n, 1, -1).filter!(isTruncatablePrime!false).front);
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}
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