How to get same value of multiple lists

osyris zosar

Lets say I have 4 lists

List<int> list1 = new List<int>();
list1.Add(4);
list1.Add(5);
list1.Add(6);
list1.Add(7);
list1.Add(9);
list1.Add(1);
List<int> list2 = new List<int>();
list1.Add(4);
list1.Add(7);
list1.Add(3);
list1.Add(0);
List<int> list3 = new List<int>();
list1.Add(0);
list1.Add(5);
List<int> list4 = new List<int>();
list1.Add(8);
list1.Add(5);
list1.Add(6);
list1.Add(7);
list1.Add(9);
list1.Add(1);
list1.Add(0);
list1.Add(3);
list1.Add(11);

i was thinking about starting with the list with the highest amount of number : list4[A] than loop to each list and see if the other lists contain that number and do A+1

so it gets to next value in the list4 until it reaches the end of the list

but there must be a more easy way that i don't know of yet

3 Replies

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Anu Viswan5y ago
Accepted answer
Believe you want to find the number which exists in all the list. You could do so with the following.
var collectionOfLists = new []{list1,list2,list3,list4};
var intersection = collectionOfLists
               .Skip(1)
               .Aggregate(new HashSet<int>(collectionOfLists.First()),
                           (hashList, item) => { hashList.IntersectWith(item); return hashList; }
                )
Kiran Mohanty5y ago
Hi ,
if you are looking for duplicate items, please add below code.
using System.Collections.Generic;
using System.Linq;


list1.AddRange(list2);
    list1.AddRange(list3);
    list1.AddRange(list4);

    var duplicates= list1.Where((x,i) => list1.IndexOf(x) != i).ToArray();
    Console.WriteLine(string.Join(",",duplicates.Distinct()));
output - 4,7,0,5,6,9,1,3
Sachin Singh5y ago
you just need to use Union to merge all elements of all Lists which automatically removes the repeated element.
var res=List1.Union(List2).Union(List3).Union(List4);
op:- 0,1,2,3,4,5,6,7,8,9,11