3n+1问题

普通循环代码（c语言）

size_t treeN (size_t i)
{
    if (i < 1)
    {
        return 0;
    }
    size_t num = 1;
    size_t n = i;
    printf("%d
",n);
    while (n != 1)
    {
        if (n % 2 == 0)
        {
            n = n / 2 ;
        }else
        {
            n = 3 * n + 1;
        }
        num ++;
        printf("%d
",n);
    }
    return num;
}

数组递归调用

size_t treeN2(int* p,int n)
{
    int* position = p;
    size_t L = 1;
    int number = n;

    while (number >= n)
    {
        if (number % 2 == 0)
        {
            number = number / 2;
        }else
        {
            number = number * 3 + 1;
        }
        L++;
    }

    if (*(p+number) == 0)
    {
        if (number % 2 == 0)
        {
            *(p+number) = treeN2(p,number/2) + L;
        }else
        {
            *(p+number) = treeN2(p,number * 3 + 1) + L;
        }
        
    }

    return *(p+number);
}

主函数

int main()
{
    int res1  = treeN(100);
    int a[100] = {0}; //先创建一个所求数大小的数组
    a[1] = 1; // 将1位置初始化为1
    int res2 = treeN2(a,100) + 1; 

    return 0;
}