From 3fc0ef8d9e271ebc5e34e28972d4ed646833623a Mon Sep 17 00:00:00 2001
From: Jesse Luehrs <doy@tozt.net>
Date: Fri, 16 Nov 2012 20:58:59 -0600
Subject: another solution

---
 SPEC.pl | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 SPEC.pl

diff --git a/SPEC.pl b/SPEC.pl
new file mode 100644
index 0000000..99ae1b9
--- /dev/null
+++ b/SPEC.pl
@@ -0,0 +1,43 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+use 5.016;
+
+my %mass = qw(
+    A   71.03711
+    C   103.00919
+    D   115.02694
+    E   129.04259
+    F   147.06841
+    G   57.02146
+    H   137.05891
+    I   113.08406
+    K   128.09496
+    L   113.08406
+    M   131.04049
+    N   114.04293
+    P   97.05276
+    Q   128.05858
+    R   156.10111
+    S   87.03203
+    T   101.04768
+    V   99.06841
+    W   186.07931
+    Y   163.06333 
+);
+
+my %protein = map {
+    val($mass{$_}) - 1 => $_,
+    val($mass{$_})     => $_,
+    val($mass{$_}) + 1 => $_,
+} keys %mass;
+
+chomp(my $prev = <>);
+while (<>) {
+    chomp;
+    my $diff = val($_) - val($prev);
+    print $protein{$diff};
+    $prev = $_;
+}
+
+sub val { int($_[0] * 10000 + 0.5) }
-- 
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