From 8162a46091d9f187bddbbde3eb6cf7f40e5fa7dd Mon Sep 17 00:00:00 2001
From: Thraix <thraix@hotmail.com>
Date: Mon, 31 Aug 2026 20:51:09 +0200
Subject: [PATCH] Add solution for 2016 Day 18

---
 res/2016/day18/test_input.txt |  1 +
 src/2016/Day18.cpp            | 46 +++++++++++++++++++++++++++--------
 2 files changed, 37 insertions(+), 10 deletions(-)

diff --git a/res/2016/day18/test_input.txt b/res/2016/day18/test_input.txt
index e69de29..ff2880a 100644
--- a/res/2016/day18/test_input.txt
+++ b/res/2016/day18/test_input.txt
@@ -0,0 +1 @@
+.^^.^.^^^^
diff --git a/src/2016/Day18.cpp b/src/2016/Day18.cpp
index 802a0ef..48695bb 100644
--- a/src/2016/Day18.cpp
+++ b/src/2016/Day18.cpp
@@ -2,30 +2,56 @@
 
 namespace y2016::day18
 {
-  REGISTER_DAY(2016, Day18, std::vector<int>, int);
+  REGISTER_DAY(2016, Day18, std::string, int);
 
-  REGISTER_TEST_EXAMPLE(2016, Day18, ExampleInput, 1, 0);
-  REGISTER_TEST(2016, Day18, Input, 1, 0);
-  REGISTER_TEST_EXAMPLE(2016, Day18, ExampleInput, 2, 0);
-  REGISTER_TEST(2016, Day18, Input, 2, 0);
+  REGISTER_TEST_EXAMPLE(2016, Day18, ExampleInput, 1, 38);
+  REGISTER_TEST(2016, Day18, Input, 1, 1913);
+  REGISTER_TEST_EXAMPLE(2016, Day18, ExampleInput, 2, 1935478);
+  REGISTER_TEST(2016, Day18, Input, 2, 19993564);
 
   READ_INPUT(input)
   {
-    std::vector<int> vec;
     std::string str;
-    while (getline(input, str))
+    getline(input, str);
+    return str;
+  }
+
+  int Solve(const std::string& str, int rows)
+  {
+    int safes = std::count(str.begin(), str.end(), '.');
+    std::vector<char> row(str.size() + 2, false);
+    for (int i = 0; i < str.size(); i++)
+      row[i + 1] = str[i] == '^';
+
+    for (int i = 1; i < rows; i++)
     {
+      std::vector<char> newRow(row.size(), false);
+      for (int j = 1; j < newRow.size() - 1; j++)
+      {
+        bool isTrap = false;
+        if (row[j - 1] && row[j] && !row[j + 1])
+          newRow[j] = true;
+        else if (!row[j - 1] && row[j] && row[j + 1])
+          newRow[j] = true;
+        else if (row[j - 1] && !row[j] && !row[j + 1])
+          newRow[j] = true;
+        else if (!row[j - 1] && !row[j] && row[j + 1])
+          newRow[j] = true;
+        else
+          safes++;
+      }
+      row = newRow;
     }
-    return vec;
+    return safes;
   }
 
   OUTPUT1(input)
   {
-    return 0;
+    return Solve(input, isExample ? 10 : 40);
   }
 
   OUTPUT2(input)
   {
-    return 0;
+    return Solve(input, 400000);
   }
 }