feat: solve day 3 puzzle 2

README.md

@@ -8,10 +8,10 @@ This project can also be run using the amazing [CraftOS-PC emulator](https://git
 ## Progress
 
 <!-- calendar-start -->
-#### Stars: 4/24
+#### Stars: 6/24
 
 |Mon|Tue|Wed|Thu|Fri|Sat|Sun|
 |:-:|:-:|:-:|:-:|:-:|:-:|:-:|
-|1<br>:star::star:|2<br>:star::star:|3<br>|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 -->

res/examples/day03.txt

@@ -0,0 +1,4 @@
+987654321111111
+811111111111119
+234234234234278
+818181911112111

res/stats.json

@@ -8,8 +8,8 @@
         "puzzle2": true
     },
     "day03": {
-        "puzzle1": false,
-        "puzzle2": false
+        "puzzle1": true,
+        "puzzle2": true
     },
     "day04": {
         "puzzle1": false,

src/day03/puzzle1.lua

@@ -0,0 +1,41 @@
+local utils = require("utils")
+local puzzle1 = {}
+
+function puzzle1.bankJoltages(bank)
+    local joltages = {}
+    for i=1, #bank do
+        table.insert(joltages, tonumber(bank:sub(i, i)))
+    end
+    return joltages
+end
+
+function puzzle1.findMaxJoltage(bank)
+    local maxTens = 0
+    local maxJoltage = 0
+    local joltages = puzzle1.bankJoltages(bank)
+
+    for i, tens in ipairs(joltages) do
+        if tens > maxTens then
+            for j=i+1, #joltages do
+                local ones = joltages[j]
+                local joltage = tens * 10 + ones
+                if joltage > maxJoltage then
+                    maxTens = tens
+                    maxJoltage = joltage
+                end
+            end
+        end
+    end
+    return maxJoltage
+end
+
+function puzzle1.solve(input)
+    local banks = utils.splitLines(input)
+    local totalJoltage = 0
+    for _, bank in ipairs(banks) do
+        totalJoltage = totalJoltage + puzzle1.findMaxJoltage(bank)
+    end
+    return totalJoltage
+end
+
+return puzzle1

src/day03/puzzle2.lua

@@ -0,0 +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)
+    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

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