35 lines
791 B
D
35 lines
791 B
D
import std.stdio;
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// See https://en.wikipedia.org/wiki/Divisor_function
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uint divisor_count(uint n) {
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uint total = 1;
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// Deal with powers of 2 first
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for (; (n & 1) == 0; n >>= 1) {
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++total;
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}
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// Odd prime factors up to the square root
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for (uint p = 3; p * p <= n; p += 2) {
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uint count = 1;
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for (; n % p == 0; n /= p) {
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++count;
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}
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total *= count;
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}
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// If n > 1 then it's prime
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if (n > 1) {
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total *= 2;
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}
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return total;
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}
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void main() {
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immutable limit = 100;
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writeln("Count of divisors for the first ", limit, " positive integers:");
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for (uint n = 1; n <= limit; ++n) {
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writef("%3d", divisor_count(n));
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if (n % 20 == 0) {
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writeln;
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}
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}
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}
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