D版能人多,问一个数学问题!!
- radiance咋一个回复的都没有呢
- 我是MIAOW孩子都上学了,留在家刷D版的家长不会做…小尾巴~
- fushia超出能力范围…💫
- alexandrite写段程序仿真一下吧。
- zsdicky刚好早些时间在看概率论的书,到现在都忘了
- zw963只推的出概率的方程, 接下来怎么推忘了, 再想想
lua脚算出来大约的值 31.2517058828复制代码- local sum_x = {
- [0] = 0,
- [1] = 0,
- [2] = 0.25,
- [3] = 0.375,
- }
- local prob_x = {
- [0] = 0,
- [1] = 0,
- [2] = 0.25,
- [3] = 0.125
- }
- function sum_prob(x)
- if sum_x[x] ~= nil then
- return sum_x[x]
- end
- sum_x[x] = prob(x) + sum_prob( x - 1)
- return sum_x[x]
- end
- function prob(x)
- if prob_x[x] ~= nil then
- return prob_x[x]
- end
- prob_x[x] = (1 - sum_prob(x-3))/8
- return prob_x[x]
- end
- function calc_average(n)
- local sn = 0
- for i = 1, n, 1 do
- sn = sn + i * prob(i)
- end
- return sn
- end
- local times = 1000000
- local average = calc_average(times)
- local ss = 0
- for i = 1, times, 1 do
- ss = ss + i * i * prob(i)
- end
- local variance = ss - average * average
- print(variance)
- local sum_x = {
- radiance回复8#zw963
我手算的得5.5,也不知道对不对 iOS fly ~ - zw963