检查List 值是否连续
List dansConList = new List(); dansConList[0] = 1; dansConList[1] = 2; dansConList[2] = 3; List dansRandomList = new List(); dansRandomList[0] = 1; dansRandomList[1] = 2; dansRandomList[2] = 4;
我需要一个方法,在评估上面的列表时,将为dansRandomList
返回false
对于dansRandomList
返回true
,基于事实dansConList
在其值中有一个连续的数字序列,而dansRandomList则没有(缺少值3)。
如果可能,最好使用LINQ。
我试过的:
- 为了达到最终结果,我使用了for循环并与’i’(循环计数器)进行比较以评估值,但如上所述,我想使用LINQ。
单行,只迭代直到第一个非连续元素:
bool isConsecutive = !myIntList.Select((i,j) => ij).Distinct().Skip(1).Any();
更新:几个如何工作的例子:
Input is { 5, 6, 7, 8 } Select yields { (5-0=)5, (6-1=)5, (7-2=)5, (8-3=)5 } Distinct yields { 5, (5 not distinct, 5 not distinct, 5 not distinct) } Skip yields { (5 skipped, nothing left) } Any returns false
Input is { 1, 2, 6, 7 } Select yields { (1-0=)1, (2-1=)1, (6-2=)4, (7-3=)4 } * Distinct yields { 1, (1 not distinct,) 4, (4 not distinct) } * Skip yields { (1 skipped,) 4 } Any returns true
* Select不会产生第二个4而Distinct不会检查它,因为Any会在找到第一个4之后停止。
var result = list .Zip(list.Skip(1), (l, r) => l + 1 == r) .All(t => t);
var min = list.Min(); var max = list.Max(); var all = Enumerable.Range(min, max - min + 1); return list.SequenceEqual(all);
您可以使用此扩展方法:
public static bool IsConsecutive(this IEnumerable ints ) { //if (!ints.Any()) // return true; //Is empty consecutive? // I think I prefer exception for empty list but I guess it depends int start = ints.First(); return !ints.Where((x, i) => x != i+start).Any(); }
像这样用它:
[Test] public void ConsecutiveTest() { var ints = new List {1, 2, 4}; bool isConsecutive = ints.IsConsecutive(); }
扩展方法:
public static bool IsConsecutive(this IEnumerable myList) { return myList.SequenceEqual(Enumerable.Range(myList.First(), myList.Last())); }
用途:
bool isConsecutive = dansRandomList.IsConsecutive();
这是另一个。 它支持{1,2,3,4}和{4,3,2,1}。 它测试顺序数差异等于1或-1。
Function IsConsecutive(ints As IEnumerable(Of Integer)) As Boolean If ints.Count > 1 Then Return Enumerable.Range(0, ints.Count - 1). All(Function(r) ints(r) + 1 = ints(r + 1) OrElse ints(r) - 1 = ints(r + 1)) End If Return False End Function
这是一个使用Aggregate
函数的扩展方法。
public static bool IsConsecutive(this List value){ return value.OrderByDescending(c => c) .Select(c => c.ToString()) .Aggregate((current, item) => (item.ToInt() - current.ToInt() == -1) ? item : "" ) .Any(); }
用法:
var consecutive = new List(){1,2,3,4}.IsConsecutive(); //true var unorderedConsecutive = new List (){1,4,3,2}.IsConsecutive(); //true var notConsecutive = new List (){1,5,3,4}.IsConsecutive(); //false
它仅适用于唯一列表。
List dansConList = new List (); dansConList.Add(7); dansConList.Add(8); dansConList.Add(9); bool b = (dansConList.Min() + dansConList.Max())*((decimal)dansConList.Count())/2.0m == dansConList.Sum();
警告:如果为空,则返回true。
var list = new int[] {-1,0,1,2,3}; var isConsecutive = list.Select((n,index) => n == index+list.ElementAt(0)).All (n => n);
这是一个C版本代码,我认为很容易用基于逻辑的其他语言重写它。
int isConsecutive(int *array, int length) { int i = 1; for (; i < length; i++) { if (array[i] != array[i - 1] + 1) return 0; //which means false and it's not a consecutive list } return 1; }