有時候得到了一個List,我想把它隨機排列一下順序。而且如果針對不同類型的List都能用,就要用到泛型。
其實思想很簡單,就是從原List中每次隨機取一項,添加到新的List中,並在原List中刪除。這樣重復,直到原List為空為止。
不過要注意,如果要保護原List不受變化,就必須先Copy一份List,再在Copy上進行操作
public static List<T> GetRandomList<T>(List<T> inputList) { //Copy to a array T[] copyArray = new T[inputList.Count]; inputList.CopyTo(copyArray); //Add range List<T> copyList = new List<T>(); copyList.AddRange(copyArray); //Set outputList and random List<T> outputList = new List<T>(); Random rd = new Random(DateTime.Now.Millisecond); while (copyList.Count > 0) { //Select an index and item int rdIndex = rd.Next(0, copyList.Count - 1); T remove = copyList[rdIndex]; //remove it from copyList and add it to output copyList.Remove(remove); outputList.Add(remove); } return outputList; }
可以這樣
List<T> l = new List<T>();
l.Sort(delegate(T a, T b) { return (new Random()).Next(-1, 1); });
也可以用linq
List<T> l = new List<T>();
l = l.Select(a => new { a, newID = Guid.NewGuid() }).OrderBy(b => b.newID).Select(c=>c.a).ToList();