print three lists <> using foreach

kiki

I have 3 lists like

List A=new List();
List B=new List();
List C=new List();

How can I print the contents of the lists like this:

first item of list A
first item of list B
first item of list C
second item of list A
second item of list B
second item of list C
third item of list A
third item of list B
third item of list C
....

6 Replies

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Matthew Cochran18y ago
Here's a different way to look at it with the 3.5 framework

-Matt

class Program
{
    static void Main(string[] args)
    {
        List<string> A = new List<string>(){ "1", "2", "3"};
        List<string> B = new List<string>(){"W", "X", "Y", "Z"};
        List<string> C = new List<string>(){"!", "@"};

        new List<String>[] { A, B, C }
            .Collate()
            .ForEach(val => Console.WriteLine(val));

        Console.ReadLine();
    }

}

public static class Extensions
{
    public static IEnumerable Collate(this IEnumerable<IEnumerable> items)
    {
        Int32
            i,
            length =items.Count();

        IEnumerator[]
            en = items.Convert(x => x.GetEnumerator()).ToArray();

        Boolean[]
           finished = new Boolean[length]; // set to 'false' by default

        while (finished.Contains(false))
        {
            for (i = 0; i < length; i++)
            {
                // we are finished if there are no more items in the enumerator
                finished[i] = ! en[i].MoveNext();

                if (!finished[i])
                    yield return en[i].Current;
            }
        }
    }

    public static IEnumerable Convert(this IEnumerable input, Func f)
    {
        foreach (T item in input)
            yield return f(item);
    }

    public static void ForEach(this IEnumerable items, Action act)
    {
        foreach (T item in items)
            act(item);
    }
}

0
Alan18y ago
OK, this is how I'd suggest doing that:

using System;
using System.Collections.Generic;

class Program
{
     static void Main()
     {
         List A= new List();
         A.Add("A1");
         A.Add("A2");
         List B= new List();
         B.Add("B1");
         B.Add("B2");
         B.Add("B3");
         List C= new List();
         C.Add("C1");
         C.Add("C2");
         C.Add("C3");
         C.Add("C4");
         // determine the largest element count
         int largest = Math.Max(A.Count, B.Count);
         largest = Math.Max(largest, C.Count);

         for (int i = 0; i < largest; i++)
         {
             if (i < A.Count)
                Console.WriteLine(A[i]);
             if (i < B.Count)
                Console.WriteLine(B[i]);
             if (i < C.Count)
                Console.WriteLine(C[i]);
         }
         Console.ReadKey();
      }
}

To use foreach() you'd have to 'interleave' the three Lists into a single List, so I think the for() statement is the best approach here.
0
kiki18y ago
yes, this is the idea, exactly
0
Alan18y ago
I might be able to propose something but I need to know how you'd want to deal with the 'excess' elements.

Suppose that A had 2 elements, B had 3 elements and C had 4 elements. How would you want to print that out?

Something like this may be:

A1
B1
C1
A2
B2
C2
B3
C3
C4
0
kiki18y ago
I understand this.... but the problem is, that in my program, the lists do not have the same size. Do you have something to propose for that?
I thought foreach statement was the solution to my problem because I dont need to know the sizes of the lists and because it's quicker in execution.
0
Alan18y ago
Assuming that all 3 lists have the same number of elements, you could do something like this:

using System;
using System.Collections.Generic;

class Program
{
     static void Main()
     {
         List A= new List();
         A.Add("A1");
         A.Add("A2");
         A.Add("A3");
         List B= new List();
         B.Add("B1");
         B.Add("B2");
         B.Add("B3");
         List C= new List();
         C.Add("C1");
         C.Add("C2");
         C.Add("C3");
         for (int i = 0; i < A.Count; i++)
         {
             Console.WriteLine(A[i]);
             Console.WriteLine(B[i]);
             Console.WriteLine(C[i]);
         }
         Console.ReadKey();
      }
}

I can't see how you could use foreach() here as you need to know the index of the element to be printed.
0