Day 4: Scratchcards


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  • Jummit@lemmy.one
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    11 months ago

    Nice and easy.

    Lua
    -- SPDX-FileCopyrightText: 2023 Jummit
    --
    -- SPDX-License-Identifier: GPL-3.0-or-later
    
    local function nums(str)
    	local res = {}
    	for num in str:gmatch("%d+") do
    		res[num] = true
    	end
    	return res
    end
    
    local cards = {}
    local points = 0
    for line in io.open("4.input"):lines() do
    	local winning, have = line:match("Card%s*%d+: (.*) | (.*)")
    	winning = nums(winning)
    	have = nums(have)
    	local first = true
    	local score = 0
    	local matching = 0
    	for num in pairs(have) do
    		if winning[num] then
    			matching = matching + 1
    			if first then
    				first = false
    				score = score + 1
    			else
    				score = score * 2
    			end
    		end
    	end
    	points = points + score
    	table.insert(cards, {have=have, wins=matching, count=1})
    end
    print(points)
    
    local cardSum = 0
    for i, card in ipairs(cards) do
    	cardSum = cardSum + card.count
    	for n = i + 1, i + card.wins do
    		cards[n].count = cards[n].count + card.count
    	end
    end
    print(cardSum)