Given a function rand7 which generates a uniform random integer in the range 1 to 7, write a function rand10 which generates a uniform random integer in the range 1 to 10.
Do NOT use system‘s Math.random().
Example 1:
Input: 1
Output: [7]
Example 2:
Input: 2
Output: [8,4]
Example 3:
Input: 3
Output: [8,1,10]
Runtime: 88 ms, faster than 42.31% of C++ online submissions for Implement Rand10() Using Rand7().
不会做，好题，是一道极限近似题。
https://leetcode.com/problems/implement-rand10-using-rand7/discuss/150301/Three-line-Java-solution-the-idea-can-be-generalized-to-%22Implement-RandM()-Using-RandN()%22
class Solution {
public:
int rand10() {
int ret = 40;
while(ret >= 40) {
ret = 7 *(rand7()-1) + rand7()-1;
}
return ret%10+1;
}
};
LC 470. Implement Rand10() Using Rand7()
原文：https://www.cnblogs.com/ethanhong/p/10205371.html