C 解法, 执行用时: 12ms, 内存消耗: 920KB, 提交时间: 2022-03-09

/**
 * 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
 *
 * srand((unsigned int)time(NULL)); already set
 * rand5() is defined
 *@return a random integer in the range 1 to 7
 *
 *
 * C语言声明定义全局变量请加上static，防止重复定义
 */
int rand5()
{
    return rand()%5+1;
}

int rand7() {
    // write code here
    int ret = 5 * rand5() + rand5() - 5;
    if(ret > 21)
        return rand7();
    return ret % 7 + 1;
}

C++ 解法, 执行用时: 13ms, 内存消耗: 908KB, 提交时间: 2022-05-03

#include <random>
std::random_device
rd;  // Will be used to obtain a seed for the random number engine
std::mt19937 gen(rd()); // Standard mersenne_twister_engine seeded with rd()
std::uniform_int_distribution<> distrib(1, 5);
class Solution {
  public:
    /**
     * 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
     */
    int rand5() {
        return distrib(gen);
    }
    int rand7() {
        // write code here
        int x = (rand5() - 1) * 5 + rand5() - 1;
        while (x > 20) {
            x = (rand5() - 1) * 5 + rand5() - 1;
        }
        return x % 7 + 1;
    }
};

C++ 解法, 执行用时: 14ms, 内存消耗: 928KB, 提交时间: 2022-03-07

#include <random>
std::random_device rd;  // Will be used to obtain a seed for the random number engine
std::mt19937 gen(rd()); // Standard mersenne_twister_engine seeded with rd()
std::uniform_int_distribution<> distrib(1, 5);
class Solution {
public:
    /**
     * 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
     */
    int rand5(){
        return distrib(gen);
    }
    int rand7() {
        // write code here
        int x=22;
        while(x>21){
            x=(rand5()-1)*5+rand5();
        }
        return x%7+1;
    }
};

C++ 解法, 执行用时: 14ms, 内存消耗: 1028KB, 提交时间: 2022-04-07

#include <random>
std::random_device rd;  // Will be used to obtain a seed for the random number engine
std::mt19937 gen(rd()); // Standard mersenne_twister_engine seeded with rd()
std::uniform_int_distribution<> distrib(1, 5);
class Solution {
public:
    /**
     * 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
     */
    int rand5(){
        return distrib(gen);
    }
    int rand7() {
        // write code here
        int x = (rand5() - 1)* 5 + rand5() - 1;
        while(x > 20) {
            x = (rand5() - 1) * 5 + rand5() - 1;
        }
        return x % 7 + 1;
    }
};

C++ 解法, 执行用时: 14ms, 内存消耗: 1036KB, 提交时间: 2022-06-23

#include <random>
std::random_device rd;  // Will be used to obtain a seed for the random number engine
std::mt19937 gen(rd()); // Standard mersenne_twister_engine seeded with rd()
std::uniform_int_distribution<> distrib(1, 5);
class Solution {
public:
    /**
     * 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
     */
    int rand5(){
        return distrib(gen);
    }
    int rand7() {
        // write code here
        int ret = rand5()+(rand5() -1)*5;
        while (ret>21)
        {
            ret = rand5()+rand5()*5;
        }
        return ret%7 + 1;
    }
};