day 9

9/README.md

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+# [Day 9](https://adventofcode.com/2022/day/9) 
+:gift::gift::gift::gift::gift::gift::gift::gift::gift:
+
+Today's language: **php**
+
+My very first php-program :v:
+```shell
+php -S localhost:8000 -t .
+firefox http://localhost:8000
+```

9/index.php

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+<h1>DER BIMMLER</h2>
+<?php
+function move_number_closer(&$headn, &$tailn) {
+    $distance = $headn - $tailn;
+    if (abs($distance) > 1) {
+        $tailn += ($distance <=> 0);
+    }
+}
+
+/* ---------- */
+/* ---H---1H- */
+/* -1----2--- */
+/* -2-------- */
+function move_tail(&$head, &$tail, $tailnr, $i) {
+    print(strval($i)."-".strval($tailnr)."Head: ");
+    print_pos($head);
+    print(": ");
+    print_pos($tail);
+
+    $dx = $head[0] - $tail[0];
+    $dy = $head[1] - $tail[1];
+    if (abs($dx) > 2 || abs($dy) > 2) {
+        exit(1);
+    }
+    if (abs($dx) == 2)  {  // move both
+        if (abs($dy) >= 1) {
+            $tail[1] += ($dy <=> 0);
+        }
+        $tail[0] += ($dx <=> 0);
+    } 
+    else if (abs($dy) == 2) {
+        if (abs($dx) >= 1) {
+            $tail[0] += ($dx <=> 0);
+        }
+        $tail[1] += ($dy <=> 0);
+    }
+    /* move_number_closer($head[0], $tail[0]); */
+    /* move_number_closer($head[1], $tail[1]); */
+    print("->");
+    print_pos($tail);
+    print("<br>");
+}
+
+function print_pos($pos) {
+    print("[".strval($pos[0]).",".strval($pos[1])."]");
+}
+
+$display_lines = array();
+function display($head, $tail) {
+    ob_clean();
+    $req_size_x = max($head[0], $tail[0]);
+    $req_size_y = max($head[1], $tail[1]);
+    for ($y = 0; $y < $req_size_y; $y++) {
+        $display_lines[$y] = str_repeat('.', $req_size_x);
+    }
+    $display_lines[$head[1]][$head[0]] = "H";
+    $display_lines[$tail[1]][$tail[0]] = "T";
+    for ($y = 0; $y < count($display_lines); $y++) {
+        print($display_lines[$y]."<br>");
+    }
+}
+
+$filename = "ropes.txt";
+/* $filename = "test2.txt"; */
+$ropefile = fopen($filename, "r");
+$input = fread($ropefile, filesize($filename));
+$head_movements = explode("\n", $input);
+fclose($ropefile);
+
+$visited_positions = array("0_0" => 0);
+$current_positions = array_fill(0, 10, [0, 0]);
+
+for ($i = 0; $i < count($head_movements); $i++) {
+    /* print($head_movements[$i]); */
+    $direction = $head_movements[$i][0];
+    $amount = (int) substr($head_movements[$i], 2);
+
+    for ($a = 0; $a < $amount; $a++) {
+        // move head
+        switch ($direction) {
+            case "L":
+                $current_positions[0][0] -= 1;
+                break;
+            case "R":
+                $current_positions[0][0] += 1;
+                break;
+            case "U":
+                $current_positions[0][1] += 1;
+                break;
+            case "D":
+                $current_positions[0][1] -= 1;
+                break;
+        }
+        // move tails
+        for ($t = 1; $t < count($current_positions); $t++) {
+            move_tail($current_positions[$t-1], $current_positions[$t], $t, $i);
+        }
+        $last_tail = count($current_positions) - 1;
+        $visited_positions[strval($current_positions[$last_tail][0])."_".strval($current_positions[$last_tail][1])] += 1;
+        /* display($current_positions[0], $current_positions[$last_tail]); */
+    }
+}
+print_r($visited_positions);
+print("Total number of positions=".array_sum($visited_positions));
+print("Number of unique visited positions=".count($visited_positions));