Merge pull request #3788 from E7-87-83/master

Challenge 105 Task 1

1 files changed, 78 insertions, 0 deletions

diff --git a/challenge-105/cheok-yin-fung/perl/ch-1.pl b/challenge-105/cheok-yin-fung/perl/ch-1.pl
new file mode 100644
index 0000000000..3a8ab8c2f5
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+++ b/challenge-105/cheok-yin-fung/perl/ch-1.pl
@@ -0,0 +1,78 @@
+#!/usr/bin/perl 
+# The Weekly Challenge 105
+# Task 1: Nth Root
+# Usage: ch-1.pl $N $k
+
+# $N positive integer, $k positive number
+# Accuracy up to 2 decimal places
+
+use strict;
+use warnings;
+
+my $pow = 1;
+my $N = int $ARGV[0];
+my $k = $ARGV[1];
+
+print "WARN: Recommend to take the result from Newton's method if two methods dispute";
+print "WARN: N is large; probably dispute between two methods \n"
+    if $N > 9;         # parameter chosen by testing
+print "WARN: N is too large; probably inaccurate result(s) \n" 
+    if $N > 100;
+print "WARN: k is too small against N; probably output errors \n" 
+    if $k/$N < 0.05;
+
+
+sub lazy_root {
+# I like math, but being ultralazy, 
+# thought of settling with the task by junior school math
+    my $puppet_k = $k * (100**$N);
+    my $i = 0;
+
+    while ($pow < $puppet_k) {
+        $i++;
+        $pow = $i**$N;
+    }
+
+    if ($pow > $puppet_k) {
+        my $pow_smaller = ($i-1)**$N;
+        $i = $i-1 if ($pow - $puppet_k) > ($puppet_k - $pow_smaller);
+    }
+
+    $i = $i/100.0;
+
+    if ($pow == $puppet_k) {
+        print "$i\n";
+    }
+    else {
+        printf "%.2f\n",$i;
+    }
+}
+
+sub newton_root {
+    my @x;
+    $x[0] = $N > 20 ? sqrt($k)/$N : sqrt($k);
+    my $dff = 0.0005;  # error terms computable 
+                       # but too lazy to check Numerical Analysis textbook
+    my $t = 0;
+    while ($dff >= 0.0005) {
+        $dff = $x[$t]**$N - $k;
+        $x[$t+1] = $x[$t] - ( $dff / $x[$t]**($N-1) / $N);
+        $t++;
+    }
+
+    my $puppet_x = sprintf "%.2f", $x[$t];
+    if ($puppet_x**$N==$k) {
+        $puppet_x =~ s/\.([0-9])*0$/\.$1/;
+        $puppet_x =~ s/\.0$//;
+        print "$puppet_x\n";
+    }
+    else {
+        printf "%.2f\n", $x[$t];
+    }
+}
+
+print "By lazy method:\n";
+lazy_root();
+
+print "By Newton's method:\n";
+newton_root();