如何比较数组中的值

Question

If you have a string of "1,2,3,1,5,7" you can put this in an array or hash table or whatever is deemed best.

How do you determine that all value are the same? In the above example it would fail but if you had "1,1,1" that would be true.

Answer 1

This can be done nicely using lambda expressions.

For an array, named arr :

var allSame = Array.TrueForAll(arr, x => x == arr[0]);

For an list ( List<T> ), named lst :

var allSame = lst.TrueForAll(x => x == lst[0]);

And for an iterable ( IEnumerable<T> ), named col :

var first = col.First();
var allSame = col.All(x => x == first);

Note that these methods don't handle empty arrays/lists/iterables however. Such support would be trivial to add however.

Answer 2

Iterate through each value, store the first value in a variable and compare the rest of the array to that variable. The instant one fails, you know all the values are not the same.

Answer 3

How about something like...

string numArray = "1,1,1,1,1";
return numArrray.Split( ',' ).Distinct().Count() <= 1;

Answer 4

I think using List<T>.TrueForAll would be a slick approach.

http://msdn.microsoft.com/en-us/library/kdxe4x4w.aspx

Answer 5

不如简单的循环有效（因为它总是处理所有项目，即使结果可以更快地确定），但是：

if (new HashSet<string>(numbers.Split(',')).Count == 1) ...