用迭代實現無限級分類

說起那個無限級分類，相信很多人都知道是什麼東西，也曾經做過。我也相信，大家用得最多的實現方式就是做一個遞歸。

最近我也要做一個帶無限級分類的菜單，但是我又不想用遞歸來做，所以我需要用其他方式來實現，那就是迭代了。

首先，我需要定義一個實體模型，這舉一個省市無限級的例子：

    class Loaction
    {
        public int ID { get; set; }
        public int PID { get; set; }
        public string Name { get; set; }    //地方名
        public int Level { get; set; }      //深度
    }

然後寫方法，這裡需要利用到棧的後進先出的特點：

        public static List<Loaction> Soft(List<Loaction> data, int pid)
        {
            Stack task = new Stack();
            task.Push(pid);
            List<Loaction> tree = new List<Loaction>();
            int level = 0;
            while (task.Count > 0)
            {
                bool flag = false;
                for (int i = 0; i < data.Count; i++)
                {
                    var l = data[i];
                    if (l.PID == pid)
                    {
                        pid = l.ID;
                        task.Push(l.ID);
                        l.Level = level;
                        level++;
                        tree.Add(l);
                        data.Remove(l);
                        i--;
                        flag=true;
                    }
                }
                if (!flag)
                {
                    task.Pop();
                    if (task.Count > 0)
                    {
                        pid = Convert.ToInt32(task.Peek());
                        level--;
                    }
                }
            }
            return tree;
        }

最後準備數據->調用->輸出：

        static void Main(string[] args)
        {
            var data = new List<Loaction>();
            data.Add(new Loaction() { ID = 1, PID = 0, Name = "北京" });
            data.Add(new Loaction() { ID = 2, PID = 0, Name = "廣東" });
            data.Add(new Loaction() { ID = 3, PID = 0, Name = "上海" });
            data.Add(new Loaction() { ID = 4, PID = 0, Name = "重慶" });
            data.Add(new Loaction() { ID = 5, PID = 0, Name = "黑龍江" });
            data.Add(new Loaction() { ID = 6, PID = 1, Name = "丰台" });
            data.Add(new Loaction() { ID = 7, PID = 1, Name = "海澱" });
            data.Add(new Loaction() { ID = 8, PID = 1, Name = "石景山" });
            data.Add(new Loaction() { ID = 9, PID = 3, Name = "上海市" });
            data.Add(new Loaction() { ID = 10, PID = 2, Name = "廣州" });
            data.Add(new Loaction() { ID = 11, PID = 5, Name = "齊齊哈爾" });
            data.Add(new Loaction() { ID = 12, PID = 2, Name = "茂名" });
            data.Add(new Loaction() { ID = 13, PID = 2, Name = "深圳" });
            data.Add(new Loaction() { ID = 14, PID = 5, Name = "哈爾濱" });
            data.Add(new Loaction() { ID = 15, PID = 4, Name = "重慶市" });
            data.Add(new Loaction() { ID = 16, PID = 2, Name = "東莞" });
            data.Add(new Loaction() { ID = 17, PID = 2, Name = "中山" });
            data.Add(new Loaction() { ID = 18, PID = 16, Name = "厚街鎮" });

            var tree = Soft(data, 0);

            foreach (var t in tree)
            {
                var sb = new StringBuilder();
                for (int i = 0; i < t.Level; i++)
                {
                    sb.Append("  ");
                   
                } 
                sb.Append(t.Name);
                Console.WriteLine(sb.ToString());
            }
            Console.ReadKey();
        }

然後效果如下：

就是這個樣子。。。。。(END)