How to find the different element of the list?

Question

C++ / C#

Suppose there is a list that is guaranteed to consist of either zeros and one unit, or ones and one zero, how can you find the index of a different element?

Answer 1

using System;
using System.Collections.Generic;
using System.Linq;

public class Program
{
    static public void Main ()
   	{
      List<int> list = new List<int>()
    {
      0, 1, 0, 0
    };
    Console.WriteLine(list.IndexOf(1));
    }
}

Answer 2

example