Merge pull request #11047 from jeanluc2020/jeanluc2020-291

Add solution 291 (only part 1)

2 files changed, 74 insertions, 0 deletions

diff --git a/challenge-291/jeanluc2020/blog-1.txt b/challenge-291/jeanluc2020/blog-1.txt
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+http://gott-gehabt.de/800_wer_wir_sind/thomas/Homepage/Computer/perl/theweeklychallenge-291-1.html
diff --git a/challenge-291/jeanluc2020/perl/ch-1.pl b/challenge-291/jeanluc2020/perl/ch-1.pl
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+#!/usr/bin/env perl
+# https://theweeklychallenge.org/blog/perl-weekly-challenge-291/#TASK1
+#
+# Task 1: Middle Index
+# ====================
+#
+# You are given an array of integers, @ints.
+#
+# Write a script to find the leftmost middle index (MI) i.e. the smallest
+# amongst all the possible ones.
+#
+## A middle index is an index where ints[0] + ints[1] + … + ints[MI-1] ==
+##  ints[MI+1] + ints[MI+2] + … + ints[ints.length-1].
+#
+# If MI == 0, the left side sum is considered to be 0. Similarly,
+# if MI == ints.length - 1, the right side sum is considered to be 0.
+#
+# Return the leftmost MI that satisfies the condition, or -1 if there is no
+# such index.
+#
+## Example 1
+##
+## Input: @ints = (2, 3, -1, 8, 4)
+## Output: 3
+##
+## The sum of the numbers before index 3 is: 2 + 3 + -1 = 4
+## The sum of the numbers after index 3 is: 4 = 4
+#
+## Example 2
+##
+## Input: @ints = (1, -1, 4)
+## Output: 2
+##
+## The sum of the numbers before index 2 is: 1 + -1 = 0
+## The sum of the numbers after index 2 is: 0
+#
+## Example 3
+##
+## Input: @ints = (2, 5)
+## Output: -1
+##
+## There is no valid MI.
+#
+############################################################
+##
+## discussion
+##
+############################################################
+#
+# Starting at the beginning, we check the left and right side sum
+# at each step. If they match, we return the index. If in the
+# end, we didn't find the index, we return -1.
+
+use strict;
+use warnings;
+use List::Util qw(sum);
+
+middle_index(2, 3, -1, 8, 4);
+middle_index(1, -1, 4);
+middle_index(2, 5);
+
+sub middle_index {
+   my @ints = @_;
+   print "Input: (" . join(", ", @ints) . ")\n";
+   foreach my $i (0..$#ints) {
+      my $l = sum(@ints[0..$i-1]) // 0;
+      my $r = sum(@ints[$i+1..$#ints]) // 0;
+      if($r == $l) {
+         return print "Output: $i\n";
+      }
+   }
+   print "Output: -1\n";
+}