Initial commit

18.jl

@@ -0,0 +1,135 @@
+include("utils.jl")
+
+function parse_value(line, index)
+    if line[index] == '['
+        parse_tuple(line, index)
+    else
+        digits = match(r"^[0-9]+", SubString(line, index)).match
+        index += length(digits)
+        parse(Int, digits), index
+    end
+end
+
+function parse_tuple(line, index=1)
+    @assert line[index] == '['
+    index += 1
+
+    first, index = parse_value(line, index)
+
+    @assert line[index] == ','
+    index += 1
+
+    second, index = parse_value(line, index)
+
+    @assert line[index] == ']'
+    index +=1
+
+    return Any[first, second], index
+end
+
+function parse_input(filename)
+    map(x->x[1], map(parse_tuple, non_empty_lines(filename)))
+end
+
+function split_sf(a)
+    if typeof(a) == Int64
+        if a > 9
+            Any[div(a,2),div(a,2)+rem(a,2)], true
+        else
+            a, false
+        end
+    else
+        l, changed = split_sf(a[1])
+        a[1] = l
+        if changed
+            a, true
+        else
+            r, changed = split_sf(a[2])
+            a[2] = r
+            a, changed
+        end
+    end
+end
+
+function add_left_sf(a, number)
+    if typeof(a) == Int64
+        a + number
+    else
+        a[1] = add_left_sf(a[1], number)
+        a
+    end
+end
+
+function add_right_sf(a, number)
+    if typeof(a) == Int64
+        a + number
+    else
+        a[2] = add_right_sf(a[2], number)
+        a
+    end
+end
+
+function explode_sf(a, level=1)
+    if typeof(a) == Int64
+        return a, false, 0, 0
+    end
+    if level == 5
+        @assert typeof(a[1]) == Int64 && typeof(a[2]) == Int64
+        0, true, a[1], a[2]
+    else
+        l, changed, to_left, to_right = explode_sf(a[1], level + 1)
+        if changed
+            Any[l, add_left_sf(a[2], to_right)], true, to_left, 0
+        else
+            r, changed, to_left, to_right = explode_sf(a[2], level + 1)
+            if changed
+                Any[add_right_sf(l, to_left), r], true, 0, to_right
+            else
+                a, false, 0, 0
+            end
+        end
+    end
+end
+
+function reduce_sf(a)
+    changed = true
+    while changed
+        a, changed = explode_sf(a)
+        if changed
+            continue
+        end
+        a, changed = split_sf(a)
+    end
+    a
+end
+
+function add_sf(a, b)
+    reduce_sf(Any[deepcopy(a), deepcopy(b)])
+end
+
+function mag_sf(a)
+    if typeof(a) == Int64
+        a
+    else
+        3 * mag_sf(a[1]) + 2 * mag_sf(a[2])
+    end
+end
+
+function solution18_1()
+    mag_sf(reduce(add_sf, parse_input("18.data")))
+end
+
+function solution18_2()
+    input = collect(parse_input("18.data"))
+    max_mag = 0
+    for a in input
+        for b in input
+            print('.')
+            max_mag = max(max_mag, mag_sf(add_sf(a, b)))
+        end
+    end
+    println("")
+    max_mag
+end
+
+solution18_2()