【高级技巧】记忆化：重复计算的缓存拦截封装

local function memoize(fn)
    local cache = {}
    return function(x)
        local hit = cache[x]
        if hit ~= nil then
            return hit
        end
        local r = fn(x)
        cache[x] = r
        return r
    end
end

local function calcPowerRaw(name)
    local total = 0
    for i = 1, 5000 do
        total = total + math.sqrt(i) * (string.len(name) % 7 + 1)
    end
    return math.floor(total)
end
local calcPower = memoize(calcPowerRaw)
print(calcPower("裁决之杖"))
print(calcPower("裁决之杖"))