Get Rand10 from Rand7

https://www.lintcode.com/problem/implement-rand10-using-rand7/description

class Solution(SolBase):
    def rand10(self):
        while True:
            rand48 = self.rand7()-1 + (self.rand7()-1)*7
            if rand48 <= 39:
                return rand48 // 4 + 1

事实上，我们只用平凑近似于10的倍数的rand即可，所以我们弄出36 再取29 最后除以3也能得到类似的结果

class Solution(SolBase):
    def rand10(self):
        while True:
            rand36 = self.rand7()-1 + (self.rand7()-1)*5
            if rand48 <= 29:
                return rand48 // 3 + 1