Count elements in array of arrays equal to specified value

Question

I have array of arrays. Suppose I want to count how much elements out of all 9 is equal to "a".

string[][] arr = new string[3][] {
    new string[]{"a","b","c"},
    new string[]{"d","a","f"},
    new string[]{"g","a","a"}
};

How can I do it using Enumerable extension methods (Count, Where, etc)?

willeM_ Van Onsem · Accepted Answer · 2017-06-15 15:13:39Z

3

You simply need a way to iterate over the subelements of the matrix, you can do this using SelectMany(), and then use Count():

int count = arr.SelectMany(x => x).Count(x => x == "a");

Producing:

csharp> arr.SelectMany(x => x).Count(x => x == "a");
4

Or you could Sum() up the counts of the Count()s of each individual row, like:

int count = arr.Sum(x => x.Count(y => y == "a"));

Producing again:

csharp> arr.Sum(x => x.Count(y => y == "a"));
4

answered Jun 15, 2017 at 15:05

willeM_ Van Onsem

482k33 gold badges483 silver badges624 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Sergey Berezovskiy · Accepted Answer · 2017-06-15 15:05:21Z

3

You can flatten all arrays into single sequence of strings with SelectMany and then use Count extension which accepts predicate:

arr.SelectMany(a => a).Count(s => s == "a")

answered Jun 15, 2017 at 15:05

237k44 gold badges441 silver badges468 bronze badges