Lua丑数：三指针生成的第n项

local function isUgly(n)
    for _, p in ipairs({2, 3, 5}) do
        while n % p == 0 do n = n / p end
    end
    return n == 1
end

local function uglyNth(n)
    local u = {1}
    local i2, i3, i5 = 1, 1, 1
    for k = 2, n do
        local a, b, c = u[i2] * 2, u[i3] * 3, u[i5] * 5
        local m = math.min(a, b, c)
        u[k] = m
        if m == a then i2 = i2 + 1 end
        if m == b then i3 = i3 + 1 end
        if m == c then i5 = i5 + 1 end
    end
    return u[n]
end
local p = getplayerbyname("ugly01")
sendmsg(p, 1, "第 1500 个丑数 " .. uglyNth(1500))