day 14, parts 1 and 2!

12023/14/14.lua

@@ -0,0 +1,169 @@
+io.input("input")
+
+r = 0
+cols = {}
+for line in io.lines() do
+    if r==0 then
+        len = #line
+        for i=1,len do
+            cols[i] = {}
+        end
+    end
+    r = r+1
+
+    for i=1,len do
+        local c = line:sub(i,i)
+        cols[i][r] = c
+    end
+end
+
+function tilt(t)
+    local cols = {}
+    table.move(t,1,#t,1,cols)
+    for i=1,len do
+        --print("\ncol"..i,table.concat(cols[i]))
+        local o,f=1,1
+        local done = false
+        while o<=len-1 do
+            --print("o",o)
+            local cs,cr = 0,0
+            local curr = cols[i][o]
+            if curr~="." then goto fixed end
+            f=o+1
+            done = false
+            repeat --search for next rock
+                --print("f",f)
+                local nxt = cols[i][f]
+                if nxt=="O" then -- swap?
+                    cols[i][o] = "O"
+                    cols[i][f] = "."
+                    --print("swapped",o,f)
+                elseif nxt=="#" then --skip
+                    o=f
+                    --print("skipped to",f)
+                end
+
+                f=f+1
+            until f>len or nxt~="."
+            if f>len then break end
+            ::fixed::
+            o=o+1
+        end
+        --print("->",table.concat(cols[i]))
+    end
+    return cols
+end
+
+function get_load(t)
+    local sum = 0
+    for i=1,len do
+        for j=1,len do
+            local c = t[j][i]
+            if c=="O" then
+                local res = len-i+1
+                sum = sum + res
+            end
+        end
+    end
+    return sum
+end
+
+function print_map(t)
+    for i=1,len do
+        local s = ""
+        for j=1,len do
+            s = s .. t[i][j]
+        end
+        print(s)
+    end
+end
+
+function encode(t)
+    local s = ""
+    for i,c in ipairs(t) do
+        s = s .. table.concat(c)
+    end
+    return s
+end
+
+
+newcols = tilt(cols)
+sum1 = get_load(newcols)
+print("part 1",sum1)
+
+
+trans = {}
+table.move(cols,1,len,1,trans)
+history = {}
+loads = {}
+repeated = 0
+exit = 0
+for n=1,1000000 do
+    --print("<N ^W")
+    newcols = tilt(trans)
+
+    -- WEST
+    --print("<W ^N")
+    for i=1,len do
+        trans[i] = {}
+        for j=1,len do
+            trans[i][j] = newcols[j][i]
+        end
+    end
+    newcols = tilt(trans)
+
+    --SOUTH
+    --print("<S ^E")
+    for i=1,len do
+        trans[i] = {}
+        for j=1,len do
+            trans[i][j] = newcols[len-j+1][len-i+1]
+        end
+    end
+    newcols = tilt(trans)
+
+    -- EAST
+    --print("<E ^S")
+    for i=1,len do
+        trans[i] = {}
+        for j=1,len do
+            trans[i][j] = newcols[j][i]
+        end
+    end
+    newcols = tilt(trans)
+
+    --NORTH
+    --print("<N ^W")
+    for i=1,len do
+        trans[i] = {}
+        for j=1,len do
+            trans[i][j] = newcols[len-j+1][len-i+1]
+        end
+    end
+    local curr_load = get_load(trans)
+    --[[
+    if n%10==1 then
+        print("N",n)
+        --print_map(trans)
+        print(curr_load)
+        print()
+    end
+    --]]
+    local s = encode(trans)
+    if not history[s] then 
+        history[s] = n
+        loads[n] = curr_load
+    else 
+        exit=n 
+        repeated = history[s]
+        break 
+    end
+end
+
+period = exit-repeated
+target = 1000000000
+rtarget = target-repeated 
+modulo = rtarget%period
+resultn = repeated + modulo
+--print(repeated, exit, period, rtarget%period)
+print("part 2", loads[resultn])

12023/14/test

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+O....#....
+O.OO#....#
+.....##...
+OO.#O....O
+.O.....O#.
+O.#..O.#.#
+..O..#O..O
+.......O..
+#....###..
+#OO..#....