Merge pull request #5001 from mattneleigh/pwc133

	new file:   challenge-133/mattneleigh/perl/ch-1.pl

1 files changed, 59 insertions, 0 deletions

diff --git a/challenge-133/mattneleigh/perl/ch-1.pl b/challenge-133/mattneleigh/perl/ch-1.pl
new file mode 100755
index 0000000000..eeb32c03d6
--- /dev/null
+++ b/challenge-133/mattneleigh/perl/ch-1.pl
@@ -0,0 +1,59 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+
+################################################################################
+# Begin main execution
+################################################################################
+
+my @numbers = (10, 27, 85, 101);
+my $number;
+
+foreach $number (@numbers){
+    printf(
+        "Input: \$N = %d\nOutput: %d\n\n",
+        $number,
+        isqrt($number)
+    );
+}
+
+exit(0);
+################################################################################
+# End main execution; subroutines follow
+################################################################################
+
+
+################################################################################
+# Calculate the integer square root (that is to say, the largest integer less
+# than or equal to the square root) of a supplied integer 
+# Takes one argument:
+# * A positive integer
+# Returns on success:
+# * The integer square root of the supplied integer
+# Returns on error:
+# * undef if a negative number is supplied
+# Lazily adapted from an algorithm described at
+# https://en.wikipedia.org/wiki/Integer_square_root
+################################################################################
+sub isqrt{
+    my $n = int(shift());
+
+    my $small_candidate;
+    my $large_candidate;
+
+    return(undef) if($n < 0);
+    return($n) if($n < 2);
+
+    $small_candidate = isqrt($n >> 2) << 1;
+    $large_candidate = $small_candidate + 1;
+    if(($large_candidate * $large_candidate) > $n){
+        return($small_candidate);
+    } else{
+        return($large_candidate);
+    }
+
+}
+
+
+