🎉 Hello world

.gitignore

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+input.txt
+/.idea

day_1/part_1.php

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+<?php
+
+$masses = explode(',', file_get_contents('input.txt'));
+
+echo array_sum(
+    array_map(function($mass) {
+        return floor($mass / 3) - 2;
+    }, $masses)
+);

day_1/part_2.php

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+<?php
+
+$masses = explode(',', file_get_contents('input.txt'));
+
+function get_fuel_from_mass($mass)
+{
+    return floor($mass / 3) - 2;
+}
+
+echo array_sum(
+    array_map(function($mass) {
+        $total_fuel = 0;
+        while($mass > 0) {
+            $mass = max(get_fuel_from_mass($mass), 0);
+            $total_fuel += $mass;
+        }
+        return $total_fuel;
+    }, $masses)
+);

day_2/part_1.php

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+<?php
+$input = explode(',', file_get_contents('input.txt'));
+
+// don't forget : 12 @ position 1 && 2 @ position 2
+
+$i = 0;
+while($input[$i] !== 99) {
+    [$operation, $first, $second, $position] = array_slice($input, $i, 4);
+    switch ($operation) {
+        case 1:
+            $input[$position] = $input[$first] + $input[$second];
+            break;
+        case 2:
+            $input[$position] = $input[$first] * $input[$second];
+            break;
+        case 99:
+            echo $input[0];
+            exit;
+        default:
+            echo 'unknown operation : '.$operation;
+            exit;
+    }
+    $i += 4;
+}
+
+echo $input[0];

day_2/part_2.php

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+<?php
+
+$input = explode(',', file_get_contents('input.txt'));
+
+function run_opcode(array $input)
+{
+    $i = 0;
+    while ($input[$i] !== 99) {
+        [$operation, $first, $second, $position] = array_slice($input, $i, 4);
+        switch ($operation) {
+            case 1:
+                $input[$position] = $input[$first] + $input[$second];
+                break;
+            case 2:
+                $input[$position] = $input[$first] * $input[$second];
+                break;
+            case 99:
+                return $input[0];
+            default:
+                echo 'unknown operation : '.$operation;
+                exit;
+        }
+        $i += 4;
+    }
+
+    return $input[0];
+}
+
+$noun = 0;
+$verb = 0;
+while ($verb !== 99) {
+    $noun = 0;
+    while ($noun !== 99) {
+        $clone_input = $input;
+        $clone_input[1] = $noun;
+        $clone_input[2] = $verb;
+        $magic_number = run_opcode($clone_input);
+        if ($magic_number === 19690720) {
+            echo sprintf('noun : %s | verb : %s', $noun, $verb);
+        }
+        $noun++;
+    }
+    $verb++;
+}
+
+echo sprintf("\n".'answer : %u', ((100*$noun)+$verb));

day_4/part_1.php

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+<?php
+
+[$min, $max] = explode('-', file_get_contents('input.txt'));
+
+/**
+ * @param int|string $big_number
+ *
+ * @return bool
+ */
+function has_at_least_two_adjacent_number($big_number)
+{
+    $big_number = (string) $big_number;
+    $current_number = null;
+    for ($i = 0, $l = strlen($big_number); $i < $l; $i++) {
+        if ($current_number === $big_number[$i]) {
+            return true;
+        }
+        $current_number = $big_number[$i];
+    }
+
+    return false;
+}
+
+/**
+ * @param int|string $big_number
+ * @return bool
+ */
+function never_decrease($big_number)
+{
+    $big_number = (string) $big_number;
+    $current_number = null;
+    for ($i = 0, $l = strlen($big_number); $i < $l; $i++) {
+        if ($current_number > $big_number[$i]) {
+            return false;
+        }
+        $current_number = $big_number[$i];
+    }
+
+    return true;
+}
+
+/**
+ * @param int|string $number
+ *
+ * @return bool
+ */
+function is_valid($number)
+{
+    return has_at_least_two_adjacent_number($number) && never_decrease($number);
+}
+
+$valids = [];
+for ($i = $min; $i <= $max; $i++) {
+    if (is_valid($i)) {
+        $valids[] = $i;
+    }
+}
+
+echo count($valids);

day_4/part_2.php

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+<?php
+
+[$min, $max] = explode('-', file_get_contents('input.txt'));
+
+/**
+ * @param int|string $big_number
+ *
+ * @return bool
+ */
+function has_no_more_than_two_adjacent_number($big_number)
+{
+    $big_number = (string) $big_number;
+    $current_numbers = [];
+    for ($i = 0, $l = strlen($big_number); $i < $l; $i++) {
+        if (!in_array($big_number[$i], $current_numbers, true)) {
+            if (count($current_numbers) === 2) {
+                return true;
+            }
+            $current_numbers = [$big_number[$i]];
+        } else {
+            $current_numbers[] = $big_number[$i];
+        }
+    }
+
+    return count($current_numbers) === 2;
+}
+
+/**
+ * @param int|string $big_number
+ * @return bool
+ */
+function never_decrease($big_number)
+{
+    $big_number = (string) $big_number;
+    $current_number = null;
+    for ($i = 0, $l = strlen($big_number); $i < $l; $i++) {
+        if ($current_number > $big_number[$i]) {
+            return false;
+        }
+        $current_number = $big_number[$i];
+    }
+
+    return true;
+}
+
+/**
+ * @param int|string $number
+ *
+ * @return bool
+ */
+function is_valid($number)
+{
+    return has_no_more_than_two_adjacent_number($number) && never_decrease($number);
+}
+
+$valids = [];
+for ($i = $min; $i <= $max; $i++) {
+    if (is_valid($i)) {
+        $valids[] = $i;
+    }
+}
+
+echo count($valids); // more than 574 & less than 1099