Lua最长公共前缀：逐列比较的纵向扫描

local function prefix(list)
    local p = list[1]
    for i = 2, #list do
        while string.sub(p, 1, #p) ~= string.sub(list[i], 1, #p) do
            p = string.sub(p, 1, #p - 1)   -- 每次整段截取比较，开销大
        end
    end
    return p
end

local function prefix(list)
    local base = list[1]
    for c = 1, #base do
        local ch = string.byte(base, c)
        for i = 2, #list do
            if string.byte(list[i], c) ~= ch then
                return string.sub(base, 1, c - 1)
            end
        end
    end
    return base
end
sendmsg(actor, 1, "公共前缀："
    .. prefix({"矿石甲", "矿石乙", "矿石丙"}))