470. Implement Rand10() Using Rand7()

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]

 

Note:

1. rand7 is predefined.
2. Each testcase has one argument: n, the number of times that rand10 is called.

 

Follow up:

1. What is the expected value for the number of calls to rand7() function?
2. Could you minimize the number of calls to rand7()?

参考资料：here。

// The rand7() API is already defined for you.
// int rand7();
// @return a random integer in the range 1 to 7

class Solution {
public:
	int rand10() {
		int idx;
		do {
			int row = rand7();
			int col = rand7();
			idx = col + (row - 1) * 7;
		} while (idx > 40);
		return 1 + idx % 10;
	}
};

 

来源：CSDN

作者：李歇特冯·兹拜因巴哈

链接：https://blog.csdn.net/m0_37518259/article/details/103889185