From f964f370ee06115506072223ac15264646097aed Mon Sep 17 00:00:00 2001
From: mid-kid <esteve.varela@gmail.com>
Date: Mon, 16 Dec 2019 18:26:18 +0100
Subject: [PATCH] Add day 16

---
 d16.lua       | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++
 d16_input.txt |  1 +
 2 files changed, 76 insertions(+)
 create mode 100644 d16.lua
 create mode 100644 d16_input.txt

diff --git a/d16.lua b/d16.lua
new file mode 100644
index 0000000..d8f2767
--- /dev/null
+++ b/d16.lua
@@ -0,0 +1,75 @@
+signal = {}
+file = io.open(arg[1])
+for num in file:read("a"):gmatch("%d") do
+    table.insert(signal, tonumber(num))
+end
+file:close()
+
+function calc(signal, num)
+    local fin = #signal
+    local cur = num
+    local val = 0
+    while cur <= fin do
+        for _, x in ipairs({1, 0, -1, 0}) do
+            if x == 0 then
+                cur = cur + num
+            else
+                local cur_val = 0
+                for i = 1, num do
+                    cur_val = cur_val + signal[cur]
+                    cur = cur + 1
+                    if cur > fin then
+                        break
+                    end
+                end
+                val = val + cur_val * x
+            end
+            if cur > fin then
+                break
+            end
+        end
+    end
+
+    return math.abs(val) % 10
+end
+
+function calc_dumb_p2(signal, offset)
+    local val = 0
+    for i = #signal, offset, -1 do
+        val = (val + signal[i]) % 10
+        signal[i] = val
+    end
+end
+
+function signal_tostring(signal, start, len)
+    local str = ""
+    for i = start, len do
+        str = str .. string.format("%d", signal[i])
+    end
+    return str
+end
+
+offset = signal[1] * (10 ^ 6) + signal[2] * (10 ^ 5) + signal[3] * (10 ^ 4) + signal[4] * (10 ^ 3) + signal[5] * (10 ^ 2) + signal[6] * (10 ^ 1) + signal[7]
+signal_p2 = {}
+for i = 1, 10000 do
+    for i = 1, #signal do
+        table.insert(signal_p2, signal[i])
+    end
+end
+print(offset)
+offset = offset % #signal_p2
+print(offset)
+
+for i = 1, 100 do
+    for i = 1, #signal do
+        signal[i] = calc(signal, i)
+    end
+end
+
+print("Part 1:", signal_tostring(signal, 1, 8))
+
+for i = 1, 100 do
+    calc_dumb_p2(signal_p2, offset)
+end
+
+print("Part 2:", signal_tostring(signal_p2, offset + 1, offset + 8))
diff --git a/d16_input.txt b/d16_input.txt
new file mode 100644
index 0000000..b94743d
--- /dev/null
+++ b/d16_input.txt
@@ -0,0 +1 @@
+59717513948900379305109702352254961099291386881456676203556183151524797037683068791860532352118123252250974130706958763348105389034831381607519427872819735052750376719383812473081415096360867340158428371353702640632449827967163188043812193288449328058464005995046093112575926165337330100634707115160053682715014464686531460025493602539343245166620098362467196933484413717749680188294435582266877493265037758875197256932099061961217414581388227153472347319505899534413848174322474743198535953826086266146686256066319093589456135923631361106367290236939056758783671975582829257390514211329195992209734175732361974503874578275698611819911236908050184158