Comparing linkedlists c#

Question

I am having trouble comparing two linked lists, I have 2 lists for arguments sake list1 contains {1,2,3,4,5} and list2 contains {1,3,4,5,6}

I am not using linkedlistnodes for a start which is why I am asking the question here, I did try switch to notes but a lot of my other work would then have to be re-written to make it work which I don't really want to do.

Anyway here is my code thus far, I am trying to use 2 loops to cycle and compare each value. The problem is that it doesn't work in the way I intended as I didn't think that it will compare the first value of list1 against all values in list2 before moving on. It stumped me how to get this working or if I am even going about it in the right way.

bool c = false;
foreach (int s in list1) {
    foreach (int t in list2)
        if (s == t) {
            c = true;
            //The console write line in this part of the code is for testing
            Console.WriteLine("Both Lists Match  {0}, {1}", s, t);
            break;
        } else {
            c = false;
            //The console write line in this part of the code is for testing
            Console.WriteLine("Not a Match {0}, {1}", s, t);
        }
}

if (c == true) {
   Console.WriteLine("Both Lists Match");
} else {
    Console.WriteLine("Not a Match");
}

Answer 1

You indicated that "i am simply trying to test if all elements of list1 are in list2".

This can be solved using two nested loops where you compare the elements of the list, as you are trying with the code you have posted with your question, but there are a few problems with the posted code.

In terms of approach, the easiest way of thinking about this problem might be:

1. Assume list2 contains all elements from list1
2. Compare each element s in list1 with the elements t in list2
3. If s != t, for each t in list2, you know the assumption was not true and you can stop searching.

You could solve this (making minimal changes to your existing code), in the following manner:

    bool c = true; // assume each 's' is in 'list2'
    foreach (int s in list1)
    {
        bool contains_s = false; // 's' in 'list2' ?
        foreach (int t in list2)
        {
            if (s == t)
            {
                // found 's' in 'list2'.
                contains_s = true;
                //The console write line in this part of the code is for testing
                Console.WriteLine("Both Lists Match  {0}, {1}", s, t);
                break; // breaks out of the inner loop.
            }
        }
        if (!contains_s) // if 's' not found we are done.
        {
            c = false;
            break; // breaks out of the outer loop
        }
    }

    if (c == true)
    {
        Console.WriteLine("Both Lists Match");
    }
    else
    {
        Console.WriteLine("Not a Match");
    }

If you are using LINQ, you can replace this with a much simpler statement, that basically does the same thing as the above loop.

var doesNotContainAllElements = list1.Any(s => !list2.Contains(s));

or

var containsAllElements = list1.All(s => list2.Contains(s));