day 11!

12023/11/11.lua

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+io.input("input")
+
+galaxies = {}
+empty_rows = {}
+empty_cols = {}
+
+
+incs = {}
+r = 1
+for line in io.lines() do
+    empty_rows[r]  = true
+    for c=1,#line do
+        local char = line:sub(c,c)
+        if char=="#" then
+            local g = table.pack(r, c)
+            table.insert(galaxies, g)
+            table.insert(incs, {0,0})
+
+            empty_rows[r] = nil
+            if empty_cols[c] then empty_cols[c] = nil end
+            --print(r,c)
+        else -- empty col?
+            if r==1 then
+                empty_cols[c] = true
+            end
+        end
+    end
+    r = r+1
+end
+
+print("# galaxies", #galaxies)
+
+expansion = 1000000 -- 2 for part 1, 1000000 for part 2
+
+-- expand empty rows
+for r,_ in pairs(empty_rows) do
+    for i=1,#galaxies do
+        local gr, gc = table.unpack(galaxies[i])
+        local ir, ic = table.unpack(incs[i])
+        if gr>r then ir = ir+expansion-1 end
+        incs[i] = table.pack(ir,ic)
+    end
+end
+
+-- expand empty cols
+for c,_ in pairs(empty_cols) do
+    for i=1,#galaxies do
+        local gr, gc = table.unpack(galaxies[i])
+        local ir, ic = table.unpack(incs[i])
+        if gc>c then ic = ic+expansion-1 end
+        incs[i] = table.pack(ir,ic)
+    end
+end
+
+
+for i=1,#galaxies do
+    local r,c = table.unpack(galaxies[i])
+    local ir, ic = table.unpack(incs[i])
+    galaxies[i] = table.pack(r+ir, c+ic)
+    --print(r+ir,c+ic)
+end
+
+sum1 = 0
+for i=1,#galaxies do
+    local g1r, g1c = table.unpack(galaxies[i])
+    for j=i+1,#galaxies do
+        local g2r, g2c = table.unpack(galaxies[j])
+        local dist = math.abs(g2r-g1r)+math.abs(g2c-g1c)
+        sum1 = sum1 + dist
+--        print(i,j, dist)
+    end
+end
+
+print("result", sum1)

12023/11/test

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+...#......
+.......#..
+#.........
+..........
+......#...
+.#........
+.........#
+..........
+.......#..
+#...#.....