From 3d45e8bf1bcd0c7ea7dab900b74b510f120180e4 Mon Sep 17 00:00:00 2001
From: Folkert Kevelam <contact@pyllr.nl>
Date: Sun, 9 Feb 2025 21:19:53 +0100
Subject: [PATCH] Initial commit

---
 AoC/2024/perl/day_1.pl | 161 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 161 insertions(+)
 create mode 100644 AoC/2024/perl/day_1.pl

diff --git a/AoC/2024/perl/day_1.pl b/AoC/2024/perl/day_1.pl
new file mode 100644
index 0000000..0ad2e35
--- /dev/null
+++ b/AoC/2024/perl/day_1.pl
@@ -0,0 +1,161 @@
+#!/usr/bin/perl
+use v5.40;
+
+sub day1_1( $filename ) {
+    open(my $FH, '<', $filename) or die $!;
+
+    my @list1;
+    my @list2;
+
+    my $counter = 0;
+    while(<$FH>) {
+        my @data = split(" ", $_);
+        if (@data == 2) {
+            push(@list1, $data[0]);
+            push(@list2, $data[1]);
+        } else {
+            print("More than two data points found at: $counter\n");
+            return -1;
+        }
+        $counter++;
+    }
+
+    @list1 = sort @list1;
+    @list2 = sort @list2;
+
+    if ($#list1 != $#list2) {
+        print("indices don't match\n");
+        return -1;
+    }
+
+    my $total = 0;
+    for( my $i = 0; $i<=$#list1; $i++) {
+        $total += abs($list1[$i] - $list2[$i]);
+    }
+
+    close($FH);
+
+    return $total;
+}
+
+sub round( $num ) {
+    my $base = int($num);
+    if($num - $base >= 0.5) {
+        $base++;
+    }
+
+    return $base
+}
+
+sub find_count($item, $is_sorted, @list) {
+    if($is_sorted != 1) {
+        @list = sort @list;
+    }
+
+    my $lower_bound = 0;
+    my $upper_bound = $#list;
+    my $index = 0;
+    my $found_location = 0;
+    until($found_location == 1) {
+        if ($upper_bound - $lower_bound <= 1) {
+            if ($list[$upper_bound] == $item) {
+                $index = $upper_bound;
+                last;
+            } elsif ($list[$lower_bound] == $item) {
+                $index = $lower_bound;
+                last;
+            } else {
+                return 0;
+            }
+        }
+        $index = round(($upper_bound + $lower_bound) / 2);
+        if ($list[$index] > $item) {
+            $upper_bound = $index;
+        } elsif ($list[$index] < $item) {
+            $lower_bound = $index;
+        } else {
+            last;
+        }
+    }
+
+    my $count = 1;
+
+    my $index_above = $index + 1;
+    my $index_lower = $index - 1;
+    my $index_above_found = 1;
+    my $index_lower_found = 1;
+
+    while( $index_above_found == 1 || $index_lower_found == 1 ) {
+        if($index_above_found == 1) {
+            if($list[$index_above] == $item) {
+                $count++;
+                $index_above++;
+            } else {
+                $index_above_found = 0;
+            }
+        }
+
+        if($index_lower_found == 1) {
+            if($list[$index_lower] == $item) {
+                $count++;
+                $index_lower--;
+            } else {
+                $index_lower_found = 0;
+            }
+        }
+    }
+
+    return $count;
+}
+
+sub day1_2( $filename ) {
+    open( my $FH, '<', $filename) or die $!;
+
+    my @list1;
+    my @list2;
+
+    my $counter = 0;
+    while(<$FH>) {
+        my @data = split(" ", $_);
+        if (@data == 2) {
+            push(@list1, $data[0]);
+            push(@list2, $data[1]);
+        } else {
+            print("More than two data points found at: $counter\n");
+            return -1;
+        }
+        $counter++;
+    }
+
+    if($#list1 != $#list2) {
+        print("indices don't match\n");
+        return -1;
+    }
+
+    @list1 = sort @list1;
+    @list2 = sort @list2;
+
+    my $total = 0;
+    my $prev_num = 0;
+    my $prev_count = 0;
+    foreach my $item (@list1) {
+        my $loc_count = 0;
+        if ($item == $prev_num ) {
+            $loc_count = $prev_count;
+        } else {
+            $loc_count = find_count($item, 1, @list2);
+        }
+            
+        $total += $item * $loc_count;
+        $prev_num = $item;
+        $prev_count = $loc_count;
+    }
+
+    return $total;
+}
+
+my $data = "./input_day_1_1.txt";
+my $sum = day1_1($data);
+my $simi = day1_2($data);
+print("Sum of differences: $sum\n");
+print("Similarity score: $simi\n");