using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Ropin.Inspection.Common.Helper
{
    public class ListHelper<T>
    {
        public static void RemoveNull(List<T> list)
        {
            for (int i = list.Count - 1; i >= 0; i--)
                if (list[i] == null)
                    list.RemoveAt(i); // O(n)
        }
        public static void RemoveNullTwo(List<T> list)
        {
            // 找出第一个空元素 O(n)
            int count = list.Count;
            for (int i = 0; i < count; i++)
                if (list[i] == null)
                {
                    // 记录当前位置
                    int newCount = i++;

                    // 对每个非空元素，复制至当前位置 O(n)
                    for (; i < count; i++)
                        if (list[i] != null)
                            list[newCount++] = list[i];

                    // 移除多余的元素 O(n)
                    list.RemoveRange(newCount, count - newCount);
                    break;
                }
        }
        public static List<T> RemoveNullThree(List<T> oldList)
        {
            List<T> listTemp = new List<T>();
            for (int i = oldList.Count - 1; i >= 0; i--)
                if (oldList[i] != null)
                    listTemp.Add(oldList[i]);
            return listTemp;
        }
    }
}