From bd81ae52c10c4ac2f63283dd38b2b396f518df12 Mon Sep 17 00:00:00 2001
From: Gurunandan Bhat <gbhat@pobox.com>
Date: Sat, 30 Jul 2022 21:50:16 +0530
Subject: Solution to Challenge 2 in Perl and Go

---
 challenge-175/bhat_gurunandan/go/ch-2.go   | 72 ++++++++++++++++++++++++++++++
 challenge-175/bhat_gurunandan/perl/ch-2.pl | 58 ++++++++++++++++++++++++
 2 files changed, 130 insertions(+)
 create mode 100644 challenge-175/bhat_gurunandan/go/ch-2.go
 create mode 100755 challenge-175/bhat_gurunandan/perl/ch-2.pl

diff --git a/challenge-175/bhat_gurunandan/go/ch-2.go b/challenge-175/bhat_gurunandan/go/ch-2.go
new file mode 100644
index 0000000000..70b380283b
--- /dev/null
+++ b/challenge-175/bhat_gurunandan/go/ch-2.go
@@ -0,0 +1,72 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+)
+
+func gcd(n int, m int) int {
+
+	for m != 0 {
+		n, m = m, n%m
+	}
+
+	return n
+}
+
+func totient(n int) int {
+
+	totient := 1
+
+	for this := n; this > 1; this-- {
+		if !(n%this == 0 || gcd(n, this) > 1) {
+			totient++
+		}
+	}
+
+	return totient
+}
+
+func main() {
+
+	var max int
+	var err error
+
+	if 2 == len(os.Args) {
+		max, err = strconv.Atoi(os.Args[1])
+		if err != nil {
+			log.Fatal(err)
+		}
+	} else {
+		log.Fatal("ERROR: Requires at exactly one integer argumemt")
+	}
+
+	cache := map[int]int{}
+	perfect := []int{}
+	this := 2
+
+	for len(perfect) < max {
+
+		sum, iter := 1, this
+		for iter > 1 {
+
+			if cache[iter] == 0 {
+				cache[iter] = totient(iter)
+			}
+			iter = cache[iter]
+
+			sum += iter
+		}
+
+		if this == sum {
+			perfect = append(perfect, this)
+		}
+
+		this++
+	}
+
+	fmt.Println(perfect)
+
+}
diff --git a/challenge-175/bhat_gurunandan/perl/ch-2.pl b/challenge-175/bhat_gurunandan/perl/ch-2.pl
new file mode 100755
index 0000000000..ff0b2c0a69
--- /dev/null
+++ b/challenge-175/bhat_gurunandan/perl/ch-2.pl
@@ -0,0 +1,58 @@
+#! /usr/bin/env perl
+
+use 5.36.0;
+use integer;
+
+sub _gcd ($a , $b) {
+
+    while ($b != 0) {
+		($a, $b) = ($b, $a % $b);
+	}
+
+	return $a;
+}
+
+sub totient ($n) {
+
+    my $this = $n;
+    my $totient = 1;
+
+    while (--$this > 1) {
+        #
+        # if we have no remainder, then the number is NOT relative
+        # prime and no need to calculate the gcd so decrement $this
+        # and move on
+        #
+        next if !($n % $this) ||
+                _gcd ($n, $this) > 1;
+
+        ++ $totient;
+    }
+
+    return $totient;
+}
+
+die "Needs a number\n" unless my $MAX = $ARGV [0];
+
+my %cache	= ();  # this holds any totients that we have seen before
+my @perfect = ();
+my $this	= 2;
+
+while (@perfect < $MAX) {
+
+    my $sum = 1;
+    my $totient = $this;
+    while ($totient = ($cache {$totient} //= totient ($totient))) {
+
+        $sum += $totient;
+        last if $totient == 1;
+    }
+
+    push @perfect, $this
+      if $this == $sum;
+
+    $this++;
+}
+
+say $_ + 1 . " :\t" . $perfect[$_]
+  for keys @perfect;
-- 
cgit