How to check if int occurs in list 3 times?

Question

I have a list that contains ints, all from 0-2. Now I have to check if any of these numbers occurs exactly 3 times. How would one check that?

Example:

{ 2, 1, 0, 0, 1, 0 } //this is true

{ 1, 1, 2, 0, 0 } //this is false

{ 0, 0, 0, 1, 1, 1, 2, 2, 2 } //this is true

Answer 1

You could use LINQ for this:

bool containsNum3x = 
    list
        .GroupBy(i => i) // group the 0s into a subset, the 1s into a subset, etc
        .Any(s => s.Count()  == 3); // check if the size of any subset is exactly 3

Docs:

• GroupBy
• Any
• Count

You might need to add using System.Linq in order at the top of your code file.