day 16: cleaned up a bit

12023/16/16.lua

@@ -0,0 +1,192 @@
+io.input("input")
+
+-- parse map
+local map = {}
+local r=1
+local width = 0
+for line in io.lines() do
+    width = #line
+    map[r] = {}
+    for c=1,width do
+        local char = line:sub(c,c)
+        if char:match("[^%.]") then
+            map[r][c] = char
+        end
+    end
+    r = r + 1
+end
+local height = r-1
+
+function coord(x,y)
+    return y*1000+x
+end
+
+function energize(e,x, y)
+    local c = coord(x,y)
+    e[c] = e[c] and (e[c]+1) or 1
+end
+
+function mark_energized(e, xo, yo, xf, yf)
+    if xo==xf then -- vertical
+        yo, yf = math.min(yo,yf), math.max(yo,yf)
+        yo = math.max(1,yo)
+        yf = math.min(height, yf)
+        for y=yo,yf do
+            energize(e,xo,y)
+        end
+    elseif yo==yf then --horizontal
+        xo, xf = math.min(xo, xf), math.max(xo, xf)
+        xo = math.max(1,xo)
+        xf = math.min(width, xf)
+        for x=xo,xf do
+            energize(e,x,yo)
+        end
+    end
+end
+
+function count_energized(e)
+    local count = 0
+    for c,v in pairs(e) do
+        count = count + 1
+    end
+    return count
+end
+
+function valid_beam(x, y, dx, dy)
+    if x>=1 and x<=width and y>=1 and y<=height then
+        return com(x,y,dx,dy)
+    end
+    return nil
+end
+
+function next_beams(xs,ys,dx,dy,char,conditions)
+    if not char then return nil end
+    local cond = table.concat(com(xs,ys,dx,dy),",")
+    if conditions[cond] then return nil
+    else conditions[cond] = true end
+
+    local beams = {}
+    if char=="|" then -- splitters
+        if dx~=0 then -- duplicate
+            table.insert(beams, valid_beam(xs, ys+1, 0, 1))
+            table.insert(beams, valid_beam(xs, ys-1, 0, -1))
+        elseif dy~= 0 then -- passthrough
+            table.insert(beams, valid_beam(xs, ys+dy, dx, dy))
+        end
+    elseif char=="-" then
+        if dx~=0 then -- passthrough
+            table.insert(beams, valid_beam(xs+dx, ys, dx, dy))
+        elseif dy~= 0 then -- duplicate
+            table.insert(beams, valid_beam(xs+1, ys, 1, 0))
+            table.insert(beams, valid_beam(xs-1, ys, -1, 0))
+        end
+    elseif char=="/" then --mirrors
+        if dx~=0 then
+            table.insert(beams, valid_beam(xs, ys-dx, 0, -dx))
+        elseif dy~=0 then
+            table.insert(beams, valid_beam(xs-dy, ys, -dy, 0))
+        end
+    elseif char=="\\" then
+        if dx~=0 then
+            table.insert(beams, valid_beam(xs, ys+dx, 0, dx))
+        elseif dy~=0 then
+            table.insert(beams, com(xs+dy, ys, dy, 0))
+        end
+    end
+    return beams
+end
+
+com = table.pack
+exp = table.unpack
+
+
+function activate(x, y, dx, dy)
+    local beams = {}
+    local energized = {}
+    local conditions = {}
+    table.insert(beams, com(x,y,dx,dy))
+    repeat
+        local beam = table.remove(beams)
+        local x,y,dx,dy = exp(beam)
+        --print("\nbeam", x, y, dx, dy)
+        local xf, yf = 0,0
+        local found = nil
+        --search next
+        if dx~= 0 then
+            local xm = x
+            repeat
+                if map[y][xm] then
+                    found = map[y][xm]
+                else
+                    xm = xm + dx
+                end
+            until found or xm<1 or xm>width
+            xf, yf = xm, y
+        elseif dy~= 0 then
+            local ym = y
+            repeat
+                if map[ym][x] then
+                    found = map[ym][x]
+                else
+                    ym = ym + dy
+                end
+            until found or ym<1 or ym>height
+            xf,yf = x,ym
+        end
+
+        --print("found", found, xf, yf)
+        -- mark energized
+        mark_energized(energized,x,y,xf,yf)
+        local nb = next_beams(xf, yf, dx, dy, found, conditions)
+        if nb then
+            for _, b in ipairs(nb) do
+                table.insert(beams, b)
+            end
+        end
+    until #beams==0
+
+    --[[
+    for y=1,height do
+        local s = ""
+        for x=1,width do
+            local char = energized[coord(x,y)] and "#" or "."
+            s = s..char
+        end
+        print(s)
+    end
+    --]]
+    return count_energized(energized)
+end
+
+
+print("part 1", activate(1,1,1,0))
+
+local max = 0
+local max_conds = com(0,0,0,0)
+
+-- from the top and bottom
+for x=1,width do
+    local r = activate(x,1,0,1)
+    if r>max then
+        max, max_conds = r, com(x,1,0,1)
+    end
+    r = activate(x,height,0,-1)
+    if r>max then
+        max, max_conds = r, com(x,height,0,-1)
+    end
+end
+
+-- from the left and right
+for y=1,height do
+    local r = activate(1,y,1,0)
+    if r>max then
+        max, max_conds = r, com(1,y,1,0)
+    end
+    r = activate(width,y,-1,0)
+    if r>max then
+        max, max_conds = r, com(width,y,-1,0)
+    end
+end
+
+print(table.concat(max_conds,","))
+print("part 2", max)

12023/16/test

@@ -0,0 +1,10 @@
+.|...\....
+|.-.\.....
+.....|-...
+........|.
+..........
+.........\
+..../.\\..
+.-.-/..|..
+.|....-|.\
+..//.|....