题解 | #用rand5()实现rand7()#

import java.util.*;
public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * rand5() is defined
     * @return a random integer in the range 1 to 7
     */
    
    public int rand5() {
        return 1 + (int) (Math.random() * 5);
    }

    public int rand7() {
        // write code here
        int ans = 0;
        do {
            ans = (rand01() << 2) + (rand01() << 1) + rand01();
        } while (ans == 7);
        return ans + 1;
    }

    public int rand01() {
        int tmpValue = 0;
        do {
            tmpValue = rand5();
        } while (tmpValue == 5);
        return tmpValue % 2;
    }
}