Lua最小栈：回退也能查当前最小

-- 错误：每次查最小全栈扫描，越深越慢
local function curMin()
    local m = math.huge
    for _, v in ipairs(stack) do
        if v < m then
            m = v
        end
    end
    return m
end

local stack, mins = {}, {}
local function push(v)
    stack[#stack + 1] = v
    local top = mins[#mins]
    mins[#mins + 1] = top ~= nil and top < v and top or v
end
local function pop()
    mins[#mins] = nil
    return table.remove(stack)
end
local function curMin()
    return mins[#mins]
end
push(5)
push(3)
push(7)
local label = panel:getChildByName("minText")
label:setString(tostring(curMin()))