project-euler/Sidef/816 Shortest distance among points.sf

#!/usr/bin/ruby

# Author: Trizen
# Date: 26 November 2023
# https://github.com/trizen

# Shortest Distance Among Points
# https://projecteuler.net/problem=816

# Runtime: 4 minutes, 19 seconds

func rng(n) is cached {
    n == 0 && return 290797
    powmod(__FUNC__(n-1), 2, 50515093)
}

func d(k) {

    var P = k.of {|n|
        [rng(2*n), rng(2*n + 1)]
    }

    var C1 = P.sort_by{ .head }
    var C2 = P.sort_by{ .tail }

    var min_dist = Inf

    C1.each_cons(2, {|a,b|
        var dist = hypot(a[0] - b[0], a[1] - b[1])

        if (dist < min_dist) {
            min_dist = dist
        }

    })

    C2.each_cons(2, {|a,b|

        var dist = hypot(a[0] - b[0], a[1] - b[1])

        if (dist < min_dist) {
            min_dist = dist
        }
    })

    return min_dist.round(-9)
}

assert_eq(d(14), 546446.466846479f)
assert_eq(d(1000), 14759.650571745f)
assert_eq(d(2000), 16462.444107726f)

say d(2000000)