Week 207 Task 2

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+#!/usr/bin/env perl
+# vim:set ts=4 sw=4 sts=4 et ai wm=0 nu:
+#=============================================================================
+# ch-2.pl Perl Weekly Challenge Week 207 Task 2 H-Index
+#=============================================================================
+# Copyright (c) 2023, Bob Lied
+#=============================================================================
+# You are given an array of integers containing citations a researcher has
+# received for each paper.
+# Write a script to compute the researcher’s H-Index. For more information
+# please checkout the wikipedia page.  https://en.wikipedia.org/wiki/H-index
+#
+# The H-Index is the largest number h such that h articles have at least h
+# citations each. For example, if an author has five publications, with 9, 7,
+# 6, 2, and 1 citations (ordered from greatest to least), then the author’s
+# h-index is 3, because the author has three publications with 3 or more
+# citations. However, the author does not have four publications with 4 or
+# more citations.
+#
+# Example 1 Input: @citations = (10,8,5,4,3) Output: 4
+#   Because the 4th publication has 4 citations and the 5th has only 3.
+# Example 2 Input: @citations = (25,8,5,3,3) Output: 3
+#   The H-Index is 3 because the fourth paper has only 3 citations.
+# 
+# What this amounts to is finding the largest i in a sorted array such
+# that x[i] >= i
+#=============================================================================
+
+use v5.36;
+
+use List::Util qw/first/;
+
+use Getopt::Long;
+my $Verbose = 0;
+my $DoTest  = 0;
+
+GetOptions("test" => \$DoTest, "verbose" => \$Verbose);
+exit(!runTest()) if $DoTest;
+
+say H_index( @ARGV );
+
+sub H_index(@cite)
+{
+    my @sorted = sort { $b <=> $a } @cite;
+    my $h = first { $sorted[$_] < $_+1 } 0 .. $#sorted;
+    return $h;
+}
+
+sub runTest
+{
+    use Test2::V0;
+
+    is( H_index(10,8,5,4,3), 4, "Example 1");
+    is( H_index(25,8,5,3,3), 3, "Example 2");
+    is( H_index( 1,1,1,1,1), 1, "Example 2");
+
+    done_testing;
+}
+