Lua数组旋转：三步反转实现循环位移

local function rotate(t, k)
    for _ = 1, k do
        table.insert(t, 1, table.remove(t))   -- 一次次挪，k倍开销
    end
end

local function rev(t, i, j)
    while i < j do
        t[i], t[j] = t[j], t[i]
        i, j = i + 1, j - 1
    end
end
local function rotate(t, k)
    rev(t, 1, k)
    rev(t, k + 1, #t)
    rev(t, 1, #t)                   -- 三步反转完成循环位移
end
local bag = {"a", "b", "c", "d", "e"}
rotate(bag, 2)
sendmsg(actor, 1, "背包数量 " .. #bag .. "，首位 " .. bag[1])