What is the best way to find the duplicates in a list of a list of integers (no matter what position thay are in)? I don't necessary need code just the best way to go about this problem.eg:List<List<int>> TestData = new List<List<int>>{     new List<int> { 1, 2, 3 },     new List<int> { 2, 1, 3 },     new List<int> { 6, 8, 3 },     new List<int> { 9, 2, 4 },};The idea is that this will return2x) 1,2,31x) 6,8,31x) 9,2,4I've been breaking my head over this seemingly very simple question but for some reason I can't figure it out.Hope someone is able to help, Like I said code not necessary but greatly appreciated. 
Find duplicate in a list of a list of integers
c#;algorithms;list