Lua出栈序列：模拟压栈的合法性验证

local function valid(push, pop)
    for i = 1, #push do
        if push[i] ~= pop[i] then return false end   -- 逐位比对不成立
    end
    return true
end

local function valid(push, pop)
    local stack, pi = {}, 1
    for _, v in ipairs(push) do
        stack[#stack + 1] = v
        while #stack > 0 and stack[#stack] == pop[pi] do
            stack[#stack] = nil     -- 栈顶匹配即弹出
            pi = pi + 1
        end
    end
    return #stack == 0              -- 全弹出即合法
end
sendmsg(actor, 1, "出栈序列合法："
    .. tostring(valid({1, 2, 3, 4, 5}, {4, 5, 3, 2, 1})))