C#•16mo ago

❔ Making collatz conjecture code more efficient

hello, i recently tried to make a C# program that runs the collatz conjecture on random numbers and saves the conjecture to a .txt file; however: its really inefficient and i was wondering if anyone had any suggestions on how to improve it?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Text;
using System.Linq;

namespace COLLATZCONJECTURE
{
    class Program
    {
        static void Main(string[] args)
        {
            Random randgen = new Random();
            UnicodeEncoding encoder = new UnicodeEncoding();

            Console.ReadLine();

        start:

            var values = new List<string>();

            long selectedNum = Convert.ToInt64(randgen.Next());
            long x = selectedNum;

            string localPath = (@"D:\COLLATZ\" + Convert.ToString(x) + ".txt");

            if (File.Exists(localPath)) {
                goto start;
            }

            Console.WriteLine("Input: {0}", selectedNum);
                
                while (x > 0 && x != 1)
                {
                    if (x == 1)
                    {
                    Console.WriteLine("END --- {0}", Convert.ToString(selectedNum));
                    break;
                    }
                    if (x % 2 == 0)
                    {
                        x = x / 2;
                        Console.WriteLine(Convert.ToString(x));
                        
                    }
                    else if (x % 2 != 0)
                    {
                    x = (x * 3) + 1;
                        Console.WriteLine(Convert.ToString(x));
                   
                }
                values.Add(Convert.ToString(x));
            }

            values.Add("END -- INPUT: " + Convert.ToString(selectedNum));

            File.WriteAllLines(localPath,values);

           // Console.WriteLine(values);
          //  Console.ReadKey();

            goto start;
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Text;
using System.Linq;

namespace COLLATZCONJECTURE
{
    class Program
    {
        static void Main(string[] args)
        {
            Random randgen = new Random();
            UnicodeEncoding encoder = new UnicodeEncoding();

            Console.ReadLine();

        start:

            var values = new List<string>();

            long selectedNum = Convert.ToInt64(randgen.Next());
            long x = selectedNum;

            string localPath = (@"D:\COLLATZ\" + Convert.ToString(x) + ".txt");

            if (File.Exists(localPath)) {
                goto start;
            }

            Console.WriteLine("Input: {0}", selectedNum);
                
                while (x > 0 && x != 1)
                {
                    if (x == 1)
                    {
                    Console.WriteLine("END --- {0}", Convert.ToString(selectedNum));
                    break;
                    }
                    if (x % 2 == 0)
                    {
                        x = x / 2;
                        Console.WriteLine(Convert.ToString(x));
                        
                    }
                    else if (x % 2 != 0)
                    {
                    x = (x * 3) + 1;
                        Console.WriteLine(Convert.ToString(x));
                   
                }
                values.Add(Convert.ToString(x));
            }

            values.Add("END -- INPUT: " + Convert.ToString(selectedNum));

            File.WriteAllLines(localPath,values);

           // Console.WriteLine(values);
          //  Console.ReadKey();

            goto start;
        }
    }
}

5 Replies

Doombox•16mo ago

first, please do not use goto jump statements, like basically ever beyond that there's not a whole lot more efficiency to be gained, it's a fairly fixed algorithm with not much wiggle room you should only really need while(x > 1) though, but as an optimisation that's frankly irrelevant

katze•16mo ago

yea i tried that and when i did it, it just decided "nope, im gonna become an infinite loop" so i just didnt fix it lol what should i use instead?

Doombox•16mo ago

define a method, and use return statements to break out where necessary if you need to create an infinite loop, wrap that method in while(true) (or with a break-out condition if you want to exit it at any point)

public static string collatz(string y)
{
    if (y == null)
    {
        return null;
    }

    int x = int.Parse(y); //x is my "n"
    var results = new StringBuilder();
    results.Append(x.ToString());
    int largest = x; //keep track of biggest number

    // the algorithm
    // the redundancies (like x==1.. x!= 1) are part of troubleshooting :/
    while (x > 1)
    {
        if (x % 2 == 0)
        {
            x = x / 2;
            if (x > largest)
            {
                largest = x;
            }
            if (x != 1)
            {
                results.Append(" " + x.ToString());
            }
            if (x == 1)
            {
                results.Append(" " + x.ToString());
                results.Append(" largest number was " + largest.ToString());
                return results.ToString();
            }
        }

        if (x % 2 != 0)
        {
            if (x == 1)
            {
                results.Append(" " + x.ToString());
                results.Append(" largest number was " + largest.ToString());
                return results.ToString();
            }
            x = (3 * x) + 1;
            if (x > largest)
            {
                largest = x;
            }
            results.Append(" " + x.ToString());
        }
    }
    return results.ToString();
}

public static string collatz(string y)
{
    if (y == null)
    {
        return null;
    }

    int x = int.Parse(y); //x is my "n"
    var results = new StringBuilder();
    results.Append(x.ToString());
    int largest = x; //keep track of biggest number

    // the algorithm
    // the redundancies (like x==1.. x!= 1) are part of troubleshooting :/
    while (x > 1)
    {
        if (x % 2 == 0)
        {
            x = x / 2;
            if (x > largest)
            {
                largest = x;
            }
            if (x != 1)
            {
                results.Append(" " + x.ToString());
            }
            if (x == 1)
            {
                results.Append(" " + x.ToString());
                results.Append(" largest number was " + largest.ToString());
                return results.ToString();
            }
        }

        if (x % 2 != 0)
        {
            if (x == 1)
            {
                results.Append(" " + x.ToString());
                results.Append(" largest number was " + largest.ToString());
                return results.ToString();
            }
            x = (3 * x) + 1;
            if (x > largest)
            {
                largest = x;
            }
            results.Append(" " + x.ToString());
        }
    }
    return results.ToString();
}

I can't be bothered to implement it myself so you could take some lessons from this implementation I found on StackOverflow seems to be broadly similar to yours in general though

katze•16mo ago

thanks

Accord•16mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Making collatz conjecture code more efficient