Maximal increasing sequence

Question

i tried to make a program that finds the maximal sequence of equal elements in an array. for example:

input: 2, 1, 1, 2, 3, 3, 2, 2, 2, 1

result: 2, 2, 2

using System;
using System.Collections.Generic;

class MaximalSequence
{
    static void Main()
    {
        string[] array = Console.ReadLine().Split(new[] { ", " }, StringSplitOptions.None);
        string previous = string.Empty;
        List<string> sequence = new List<string>();
        List<string> tempSequence = new List<string>();
        for (int i = 0; i < array.Length; i++)
        {
            if (array[i] != previous)
            {
                tempSequence.Add(previous);
                if (tempSequence.Count > sequence.Count)
                {
                    sequence = tempSequence;
                }
                tempSequence.Clear();
            }
            else
            {
                tempSequence.Add(previous);
            }
            previous = array[i];
        }
        Console.WriteLine(string.Join(", ", sequence));
    }
}

the problem is that for some reason on tempSequence.Clear(); both lists are cleared.

Answer 1

Like others have pointed out, List is a reference type so assignment assigns by reference. This means that both variable are changing the same underlying object (so the .Clear clears both lists).

The solution is to make a separate object with the same contents (aka a deep copy). List provides a constructor public List(IEnumerable<T> collection) that copies elements from another collection (List).

In your code, replace sequence = tempSequence; with

sequence = new List<string>(tempSequence);

See this .NET Fiddle