Lua斐波那契：递推与取模防溢出

local function fib(n)
    if n <= 2 then return 1 end
    return fib(n - 1) + fib(n - 2)   -- 指数爆炸，50项算不完
end

local M = 1000000007
local function fib(n)
    local a, b = 1, 1
    for _ = 3, n do
        a, b = b, (a + b) % M        -- 每步取模防溢出
    end
    return b
end
sendmsg(actor, 1, "背包数量格斐波那契第40项 " .. fib(40))