Description
Given the API rand7()
that generates a uniform random integer in the range [1, 7]
, write a function rand10()
that generates a uniform random integer in the range [1, 10]
. You can only call the API rand7()
, and you shouldn't call any other API. Please do not use a language's built-in random API.
Each test case will have one internal argument n
, the number of times that your implemented function rand10()
will be called while testing. Note that this is not an argument passed to rand10()
.
Example 1:
Input: n = 1 Output: [2]
Example 2:
Input: n = 2 Output: [2,8]
Example 3:
Input: n = 3 Output: [3,8,10]
Constraints:
1 <= n <= 105
Follow up:
- What is the expected value for the number of calls to
rand7()
function? - Could you minimize the number of calls to
rand7()
?
Solution
Python3
# The rand7() API is already defined for you.
# def rand7():
# @return a random integer in the range 1 to 7
class Solution:
def rand10(self):
rand40 = 40
while rand40 >= 40:
rand40 = (rand7() -1)*7 + rand7() - 1
return rand40 % 10 + 1