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816 Shortest distance among points.pl
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816 Shortest distance among points.pl
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#!/usr/bin/perl
# Author: Trizen
# Date: 26 November 2023
# https://github.com/trizen
# Shortest Distance Among Points
# https://projecteuler.net/problem=816
# Runtime: 25.038s
use 5.036;
use ntheory qw(powmod);
{
my @cache;
sub rng ($n) {
$n == 0 && return 290797;
$cache[$n] //= powmod(rng($n - 1), 2, 50515093);
}
}
sub hypot ($a, $b) {
sqrt($a**2 + $b**2);
}
sub d ($k) {
my @P = map { [rng(2 * $_), rng(2 * $_ + 1)] } (1 .. $k);
my @C1 = sort { $a->[0] <=> $b->[0] } @P;
my @C2 = sort { $a->[1] <=> $b->[1] } @P;
my $min_dist = 1e9**1e9;
foreach my $i (0 .. $#C1 - 1) {
my $p1 = $C1[$i];
my $p2 = $C1[$i + 1];
my $dist = hypot($p1->[0] - $p2->[0], $p1->[1] - $p2->[1]);
if ($dist < $min_dist) {
$min_dist = $dist;
}
}
foreach my $i (0 .. $#C2 - 1) {
my $p1 = $C2[$i];
my $p2 = $C2[$i + 1];
my $dist = hypot($p1->[0] - $p2->[0], $p1->[1] - $p2->[1]);
if ($dist < $min_dist) {
$min_dist = $dist;
}
}
sprintf('%.9f', $min_dist);
}
d(14) eq '546446.466846479' or die "error";
d(1000) eq '14759.650571745' or die "error";
d(2000) eq '16462.444107726' or die "error";
say d(2000000);