Lua去重保序：seen表的过滤写法

-- 错误：排序去重，原有的优先级顺序被打乱
table.sort(words)
for i = #words, 1, -1 do
    if words[i] == words[i - 1] then
        table.remove(words, i)
    end
end

local function dedup(list)
    local seen, out = {}, {}
    for _, v in ipairs(list) do
        if not seen[v] then
            seen[v] = true
            out[#out + 1] = v
        end
    end
    return out
end
local label = panel:getChildByName("tagText")
label:setString(table.concat(dedup({"火", "冰", "火", "雷"}), ","))