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+#!/usr/bin/env perl
+
+# Challenge 251
+#
+# Task 2: Lucky Numbers
+# Submitted by: Mohammad S Anwar
+#
+# You are given a m x n matrix of distinct numbers.
+#
+# Write a script to return the lucky number, if there is one, or -1 if not.
+#
+# A lucky number is an element of the matrix such that it is
+# the minimum element in its row and maximum in its column.
+#
+#
+# Example 1
+#
+# Input: $matrix = [ [ 3,  7,  8],
+#                    [ 9, 11, 13],
+#                    [15, 16, 17] ];
+# Output: 15
+#
+# 15 is the only lucky number since it is the minimum in its row
+# and the maximum in its column.
+#
+# Example 2
+#
+# Input: $matrix = [ [ 1, 10,  4,  2],
+#                    [ 9,  3,  8,  7],
+#                    [15, 16, 17, 12] ];
+# Output: 12
+#
+# Example 3
+#
+# Input: $matrix = [ [7 ,8],
+#                    [1 ,2] ];
+# Output: 7
+
+use Modern::Perl;
+
+my @matrix = parse_matrix("@ARGV");
+say lucky_number(@matrix);
+
+sub parse_matrix {
+    my($input) = @_;
+    my @matrix;
+    $input =~ s/^\s*\[\s*//s or die "missing starting [ in '$input'";
+    $input =~ s/\s*\]\s*$//s or die "missing ending ] in '$input'";
+    $input =~ s/^\s+//s;
+    while ($input ne '') {
+        ($input, my @row) = parse_row($input);
+        push @matrix, \@row;
+        $input =~ s/^\s*,?\s*//s;
+    }
+    return @matrix;
+}
+
+sub parse_row {
+    my($input) = @_;
+    $input =~ s/^\s*\[\s*//s or die "missing starting [ in '$input'";
+    (my $row, $input) = $input =~ /(.*?)\]\s*(.*)/s or die die "missing ending ] in '$input'";
+    my @row = split(/(?:\s|,)+/, $row);
+    return ($input, @row);
+}
+
+sub lucky_number {
+    my(@matrix) = @_;
+    for my $r (0 .. $#matrix) {
+        my $row = $matrix[$r];
+        my $c = min_col_in_row(@$row);
+        my $max_r = max_row_in_col($c, @matrix);
+        if ($r == $max_r) {
+            return $matrix[$r][$c];
+        }
+    }
+    return -1;
+}
+
+sub min_col_in_row {
+    my(@row) = @_;
+    my $min_c = 0;
+    for my $c (0 .. $#row) {
+        if ($row[$c] < $row[$min_c]) {
+            $min_c = $c;
+        }
+    }
+    return $min_c;
+}
+
+sub max_row_in_col {
+    my($c, @matrix) = @_;
+    my $max_r = 0;
+    for my $r (0 .. $#matrix) {
+        if ($matrix[$r][$c] > $matrix[$max_r][$c]) {
+            $max_r = $r;
+        }
+    }
+    return $max_r;
+}