using System.Collections.Generic;
public static void Main()
List<string> list1 = new List<string>();
list1.Add("Sunday is far away");
list1.Add("Today is Monday");
list1.Add("Tuesday is too near");
List<string> list2 = new List<string>();
var result1 = list1.Where(x => list2.Any(y => x.Contains(y))).ToList();
var result2 = list2.Where(x => list1.Any(y => y.Contains(x))).ToList();
Console.WriteLine(String.Join(",",result1));
Console.WriteLine(String.Join(",",result2));