简单的阶乘

#include <iostream>
#include <stdio.h>
using namespace std;
#define ull unsigned long long
ull JC(ull k)
{
    if (k == 1) //终止条件
        return 1;
    return JC(k - 1) * k;
}

int main()
{
    // n元素阶乘测试
    ull n;
    printf("nの阶乘，请输入n：");
    scanf("%llu", &n);
    printf("%llu", JC(n));
    return 0;
}

简单的斐波那契数列

#include <stdio.h>
#include <iostream>
#include <math.h>
using namespace std;
#define ull unsigned long long

ull fib(ull k)
{
    if (k <= 1)
        return 1;
    return fib(k - 1) + fib(k - 2);
}

int main()
{
    //斐波那契测试
    ull n;
    printf("斐波那契测试，输入n：");
    scanf("%llu", &n);
    printf("%llu", fib(n));

    return 0;
}

字符全排列测试+去重思想

#include <iostream&g