分享一个面试题

[xiaohong]

输入任务一个大于0的数字n，从1到n,报数1 2 3，1 2 3，1 2.....每报到三的人出列，依次循环，直至剩下最后一个或两个数字为止，求最后这一个或两个数字是多少?

我写了一个：
大家有更好，更有效率的也请分享下代码和思路吧

private void button1_Click(object sender, EventArgs e)
        {
            int t = Convert.ToInt32(textBox1.Text);//获取输入的数字
            List<int> lInt = new List<int>();
            for (int i = 1; i <= t; i++)
                lInt.Add(i);
            lInt = js(1, 0, lInt);//运算
            foreach (int v in lInt)
            {
                textBox2.Text += v + "\t";//输出结果
            }
        }

/// <summary>
        /// 
        /// </summary>
        /// <param name="i">报数</param>
        /// <param name="index">value下标</param>
        /// <param name="value"></param>
        /// <returns></returns>
        private List<int> js(int i, int index, List<int> value)
        {
            if (value.Count < 3)
                return value;
            if (i == 3)
            {
                value.RemoveAt(index);
                return js(i++, index, value);
            }
            else
            {
                index++;
                if (index >= value.Count)
                    index = 0;
                return js(i++, index, value);
            }
        }

[xiaohong]

上面的 js方法有点小小的错误，在这里重贴出代码

 /// <summary>
        /// 
        /// </summary>
        /// <param name="i">报数</param>
        /// <param name="index">value下标</param>
        /// <param name="value"></param>
        /// <returns></returns>
        private List<int> js(int i, int index, List<int> value)
        {
            if (value.Count < 3)
                return value;
            if (i == 3)
            {
                value.RemoveAt(index);
                return js(1, index, value);
            }
            else
            {
                index++;
                if (index >= value.Count)
                    index = 0;
                return js(++i, index, value);
            }
        }

[qxyywy]

int num = 38987;
List<int> list = new List<int>();
for (int i = 1; i <= num; i++)
{
list.Add(i);
}
int lastNum = list.FindLast(n => n % 3 == 0);
if (lastNum < num)
{
if (num % 3 == 2)
{
Response.Write((++lastNum).ToString() + "、" + (++lastNum).ToString());
}
else
{
Response.Write((++lastNum).ToString());
}
}
else
{
Response.Write((--lastNum).ToString() + "、" + (--lastNum).ToString());
}

[qxyywy]

int num = 38987;
            List<int> list = new List<int>();
            for (int i = 1; i <= num; i++)
            {
                list.Add(i);
            }
            int lastNum = list.FindLast(n => n % 3 == 0);
            if (lastNum < num)
            {
                if (num % 3 == 2)
                {
                    Response.Write((++lastNum).ToString() + "、" + (++lastNum).ToString());
                }
                else
                {
                    Response.Write((++lastNum).ToString());
                }
            }
            else
            {
                Response.Write((--lastNum).ToString() + "、" + (--lastNum).ToString());
            }

[effun]

不太明白题目的意思，是要找出已经出列的数字，还是没有出列的，还是没有出列的最后一个或二个？

[五更琉璃]

约瑟夫环问题啊 老题了

[色拉油]

约瑟夫环

[qxyywy]

[Quote=引用 3 楼 qxyywy 的回复:]

C# code
if (lastNum < num)
{
if (num % 3 == 2)
{
Response.Write((++lastNum).ToString() + "、" + (++lastNum).ToString());
}
else
{
Response.Write((++lastNum).ToString());
}
}
else
{
Response.Write((--lastNum).ToString() + "、" + (--lastNum).ToString());
}
[/code]
[/Quote]

看到刚才的代码始终觉得不舒服

int num = 38987;
            List<int> list = new List<int>();
            for (int i = 1; i <= num; i++)
            {
                list.Add(i);
            }
            int lastNum = list.FindLast(n => n % 3 == 0);
            if (lastNum < num)
            {
                if (num % 3 == 2)
                {
                    Response.Write((++lastNum).ToString() + "、" + (++lastNum).ToString());
                    return;
                }
                Response.Write((++lastNum).ToString());
                return;
            }
            Response.Write((--lastNum).ToString() + "、" + (--lastNum).ToString());
            return;