From b1efda9c7d843ce315c6646bd28855200c1e8a8a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20M=C3=A5rdbrink?= <hugo@mardbrink.se>
Date: Mon, 9 Dec 2024 18:14:31 +0100
Subject: [PATCH] Day 9

---
 d09/main.cxx | 112 ++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 106 insertions(+), 6 deletions(-)

diff --git a/d09/main.cxx b/d09/main.cxx
index 3dff4c0..5c37362 100644
--- a/d09/main.cxx
+++ b/d09/main.cxx
@@ -1,15 +1,115 @@
 #include <iostream>
-#include <fstream>
+#include <chrono>
+#include <vector>
+#include <optional>
+#include <ranges>
+#include <algorithm>
+
 
 using std::cout, std::endl;
+namespace views = std::ranges::views;
 
-int main() {
-    std::ifstream file{"../d9/input.txt"};
-    std::string line;
+constexpr const char content[] = {
+    #embed "input.txt"
+};
 
-    while (std::getline(file, line)) {
-        
+void fill_free_disk(std::vector<std::optional<int>>& disk) {
+    for(auto i{0}; i < disk.size(); i++) {
+        if(!disk[i].has_value()) {
+            for(auto j{disk.size() - 1}; j > i; j--) {
+                if(disk[j].has_value() && j > i) {
+                    disk[i] = disk[j];
+                    disk[j] = std::nullopt;
+                    break;
+                }
+            }
+        }
+    }
+}
+
+long part_1() {
+    std::vector<std::optional<int>> disk = {};
+    
+    int id_counter{1};
+    for(int i = 0; i < sizeof(content); i++) {
+        std::optional<int> id = i % 2 == 0 ? std::make_optional(i/2) : std::nullopt;
+       for(int j = 0; j < content[i] - '0'; j++) {
+           disk.push_back({id});
+       }
     }
     
+    fill_free_disk(disk);
+    
+    long checksum{0};
+    for(int i{0}; i < disk.size(); i++) {
+        if(disk[i].has_value()) { 
+            checksum += i * disk[i].value();
+        }
+    }
+
+    return checksum;
+}
+
+struct Partition {
+    std::optional<int> id;
+    int start_index;
+    int size;
+
+    bool operator==(const Partition& other) const {
+        return id == other.id && start_index == other.start_index;
+    }
+};
+long part_2() {
+    std::vector<Partition> partitions = {};
+
+    for(int i = 0; i < sizeof(content)-1; i++) {
+        std::optional<int> id = i % 2 == 0 ? std::make_optional(i/2) : std::nullopt;
+        partitions.push_back({id, i, content[i] - '0'});
+    }
+    
+   for(auto& free_space : partitions) {
+        if(!free_space.id.has_value()) {
+            for(auto& file : partitions | views::reverse) {
+                if(file.id.has_value() && file.size <= free_space.size && file.start_index > free_space.start_index) {
+                    int space_left = free_space.size - file.size;
+                    Partition move_file = file; 
+                    move_file.start_index = free_space.start_index;
+                    file.id = std::nullopt;
+
+                    if(space_left == 0) {
+                        partitions.erase(std::find(partitions.begin(), partitions.end(), free_space));
+                    } else {
+                        free_space.size = space_left;
+                        free_space.start_index += file.size;
+                    }
+                    
+                    partitions.insert(std::find(partitions.begin(), partitions.end(), free_space), move_file);
+                    break;
+                }
+            } 
+        }
+    } 
+    
+    int counter{0};
+    long checksum{0};
+    for(auto& partition : partitions) {
+       for(auto _ : views::iota(0, partition.size)) {
+           if(partition.id.has_value()) {
+                checksum += counter * partition.id.value();
+           }
+           counter++;
+       }
+    }
+    return checksum;
+} 
+
+int main() {
+    std::chrono::steady_clock::time_point begin = std::chrono::steady_clock::now();
+    auto p1_val = part_1();
+    std::chrono::steady_clock::time_point middle = std::chrono::steady_clock::now();
+    auto p2_val = part_2();
+    std::chrono::steady_clock::time_point end = std::chrono::steady_clock::now();
+    cout << "Part 1: " << p1_val << " (" << std::chrono::duration_cast<std::chrono::microseconds>(middle - begin).count() << "µs)" << endl;  
+    cout << "Part 2: " << p2_val << " (" << std::chrono::duration_cast<std::chrono::microseconds>(end - middle).count() << "µs)" << endl;
     return 0;
 }