From d0cc52fbda5c03e9840cf4bb01e55998c545ce42 Mon Sep 17 00:00:00 2001
From: LordBaryhobal <lordbaryhobal@gmail.com>
Date: Wed, 3 Dec 2025 13:15:45 +0100
Subject: [PATCH] feat: solve day 3 puzzle 2

---
 README.md             |  4 +--
 res/stats.json        |  2 +-
 src/day03/puzzle2.lua | 59 ++++++++++++++++++++++++++++++++++++++++++-
 src/lib/days.lua      |  2 +-
 4 files changed, 62 insertions(+), 5 deletions(-)

diff --git a/README.md b/README.md
index f936d71..60cc3f9 100644
--- a/README.md
+++ b/README.md
@@ -8,10 +8,10 @@ This project can also be run using the amazing [CraftOS-PC emulator](https://git
 ## Progress
 
 <!-- calendar-start -->
-#### Stars: 5/24
+#### Stars: 6/24
 
 |Mon|Tue|Wed|Thu|Fri|Sat|Sun|
 |:-:|:-:|:-:|:-:|:-:|:-:|:-:|
-|1<br>:star::star:|2<br>:star::star:|3<br>:star:|4<br>|5<br>|6<br>|7<br>|
+|1<br>:star::star:|2<br>:star::star:|3<br>:star::star:|4<br>|5<br>|6<br>|7<br>|
 |8<br>|9<br>|10<br>|11<br>|12<br>|||
 <!-- calendar-end -->
diff --git a/res/stats.json b/res/stats.json
index 1987838..359a654 100644
--- a/res/stats.json
+++ b/res/stats.json
@@ -9,7 +9,7 @@
     },
     "day03": {
         "puzzle1": true,
-        "puzzle2": false
+        "puzzle2": true
     },
     "day04": {
         "puzzle1": false,
diff --git a/src/day03/puzzle2.lua b/src/day03/puzzle2.lua
index 2f4bc9a..2af22d7 100644
--- a/src/day03/puzzle2.lua
+++ b/src/day03/puzzle2.lua
@@ -1,7 +1,64 @@
+local utils = require("utils")
+local puzzle1 = require(SRC_PATH .. "/day03/puzzle1")
 local puzzle2 = {}
 
+local cache = {}
+
+function puzzle2.findMaxJoltage(bank, joltages, n, startI)
+    startI = startI or 1
+    local key = bank:sub(startI) .. "-" .. tostring(n)
+    if cache[key] then
+        return cache[key]
+    end
+
+    local maxJoltage = 0
+    local maxDigit = 0
+
+    if startI > #joltages then
+        return nil
+    end
+
+    if n == 1 then
+        for i=startI, #joltages do
+            if joltages[i] > maxDigit then
+                maxDigit = joltages[i]
+            end
+        end
+        cache[key] = maxDigit
+        return maxDigit
+    end
+
+    local i = startI
+    while i <= #joltages do
+        local digit = joltages[i]
+        if digit > maxDigit then
+            local maxSuffix = puzzle2.findMaxJoltage(bank, joltages, n - 1, i + 1)
+            if maxSuffix ~= nil then
+                local joltage = tonumber(tostring(digit) .. tostring(maxSuffix))
+                if joltage > maxJoltage then
+                    maxDigit = digit
+                    maxJoltage = joltage
+                end
+            end
+        end
+        i = i + 1
+    end
+    if maxJoltage == 0 then
+        return nil
+    end
+    cache[key] = maxJoltage
+    return maxJoltage
+end
+
 function puzzle2.solve(input)
-    return 0
+    local banks = utils.splitLines(input)
+    local totalJoltage = 0
+    for _, bank in ipairs(banks) do
+        local joltages = puzzle1.bankJoltages(bank)
+        local max = puzzle2.findMaxJoltage(bank, joltages, 12)
+        totalJoltage = totalJoltage + max
+    end
+    return totalJoltage
 end
 
 return puzzle2
diff --git a/src/lib/days.lua b/src/lib/days.lua
index 5ec2439..ef9f84a 100644
--- a/src/lib/days.lua
+++ b/src/lib/days.lua
@@ -147,7 +147,7 @@ function Day:execPuzzle(puzzleI, data, resultKey)
     local result = puzzle.solve(data)
     local t1 = os.epoch("local")
     print(("(Executed in %.3fs)"):format((t1 - t0) / 1000))
-    print("Result:", result)
+    print(("Result: %.0f"):format(result))
     self.results[resultKey] = result
     self:saveResults()
 end