[Day 7] Optimize

Author: goggle

src/day07.jl

@@ -2,46 +2,62 @@ module Day07
 
 using AdventOfCode2024
 
-
 function day07(input::String = readInput(joinpath(@__DIR__, "..", "data", "day07.txt")))
-    test_values, numbers = parse_input(input)
-    solve(test_values, numbers)
+    test_values, numbers, concat_factors = parse_input(input)
+    return solve(test_values, numbers, concat_factors)
 end
 
 function parse_input(input)
-    data = [(x, y) for (x, y) ∈ eachsplit.(eachsplit(rstrip(input), '\n'), ':')]
-    test_values = [parse(Int, x[1]) for x ∈ data]
-    numbers = [parse.(Int, split(lstrip(x[2]))) for x ∈ data]
-    return test_values, numbers
+    lines = split(rstrip(input), '\n')
+    test_values = Int[]
+    numbers = Vector{Int}[]
+    concat_factors = Vector{Int}[]
+    
+    for line in lines
+        left, right = split(line, ':')
+        nums = parse.(Int, split(right))
+        factors = [10^ndigits(n) for n in nums]
+        push!(test_values, parse(Int, left))
+        push!(numbers, nums)
+        push!(concat_factors, factors)
+    end
+    
+    return test_values, numbers, concat_factors
 end
 
-function solve(test_values::Vector{Int}, numbers::Vector{Vector{Int}})
+function solve(test_values::Vector{Int}, numbers::Vector{Vector{Int}}, concat_factors::Vector{Vector{Int}})
     p1 = p2 = 0
-    for (test_value, nl) ∈ zip(test_values, numbers)
-        if valid_p1(test_value, nl[1], @view nl[2:end])
-            p1 += test_value
-            p2 += test_value
-        elseif valid_p2(test_value, nl[1], @view nl[2:end])
-            p2 += test_value
-        end
+    for i in eachindex(test_values)
+        nums = numbers[i]
+        isempty(nums) && continue
+        tv = test_values[i]
+        cf = concat_factors[i]
+        
+        valid1 = _valid_p1(tv, nums[1], 2, nums)
+        valid2 = valid1 ? true : _valid_p2(tv, nums[1], 2, nums, cf)
+        
+        p1 += valid1 * tv
+        p2 += (valid1 || valid2) * tv
     end
     return [p1, p2]
 end
 
-function valid_p1(goal::Int, curr::Int, remaining::AbstractArray{Int})
-    isempty(remaining) && curr != goal && return false
+@inline function _valid_p1(goal::Int, curr::Int, idx::Int, numbers::Vector{Int})
+    idx > length(numbers) && return curr == goal
     curr > goal && return false
-    curr == goal && isempty(remaining) && return true
-    return valid_p1(goal, curr + remaining[1], @view remaining[2:end]) || valid_p1(goal, curr * remaining[1], @view remaining[2:end])
+    @inbounds next_num = numbers[idx]
+    return _valid_p1(goal, curr + next_num, idx + 1, numbers) || 
+           _valid_p1(goal, curr * next_num, idx + 1, numbers)
 end
 
-function valid_p2(goal::Int, curr::Int, remaining::AbstractArray{Int})
-    isempty(remaining) && curr != goal && return false
+@inline function _valid_p2(goal::Int, curr::Int, idx::Int, numbers::Vector{Int}, concat_factors::Vector{Int})
+    idx > length(numbers) && return curr == goal
     curr > goal && return false
-    curr == goal && isempty(remaining) && return true
-    return valid_p2(goal, curr + remaining[1], @view remaining[2:end]) || valid_p2(goal, curr * remaining[1], @view remaining[2:end]) || valid_p2(goal, concat(curr, remaining[1]), @view remaining[2:end])
+    @inbounds next_num = numbers[idx]
+    @inbounds cf = concat_factors[idx]
+    return _valid_p2(goal, curr + next_num, idx + 1, numbers, concat_factors) ||
+           _valid_p2(goal, curr * next_num, idx + 1, numbers, concat_factors) ||
+           _valid_p2(goal, curr * cf + next_num, idx + 1, numbers, concat_factors)
 end
 
-concat(x::Int, y::Int) = x * 10^(length(digits(y))) + y
-
 end # module