How do I bring in numbers from a text file and do math on them in c#

Question

I am new to C#. I am trying to bring numbers from a txt file into my program and multiply them. The text file would be formatted like this:

1
2
3
4
5
6
7
8
9
10

I need the program to do 1x2x3x4x5x6x7x8x9x10=3628800.

This is a list of 2 million different numbers.

I can get it to output to a text file, just not input. I have looked around and can't really see an answer.

Thanks.

Answer 1

You can do this with few lines of code.

var lines = File.ReadLines(fileName);
var collection = new List<int>();

foreach (var line in lines)
{
   collection.AddRange(line.Split(' ').Select(n => Convert.ToInt32(n)));  
}

var result = collection.Distinct().Aggregate((i, j) => i * j); // remove distinct if you don't want eliminate duplicates.

Answer 2

You can try this

string value1 = File.ReadAllText("file.txt");
int res = 1;
var numbers = value1.Split(' ').Select(Int32.Parse).ToList();
for(int i=0;i<numbers.Count;i++)
{
    res = res * numbers[i];
}
Console.WriteLine(res);

Answer 3

var numbers = File.ReadAllText("filename.txt").Split(' ').Select(int.Parse); // Read file, split values and parse to integer
var result = numbers.Aggregate(1, (x, y) => x * y); // Perform multiplication

Answer 4

You want to multiply 2 million numbers all together, but there is a problem.

The problem is memory limitation. to hold a big number you have to use BigInteger class inside System.Numerics namespace.

You can use this reference by adding Using keyword in top of your project.

using System.Numerics;

If the compiler did not recognize Numerics then You need to add an assembly reference to System.Numerics.dll.

Your code should look like this.

string inputFilename = @"C:\intput.txt"; // put the full input file path and name here.

var lines = File.ReadAllLines(inputFilename); // put text lines into array of string.

BigInteger big = new BigInteger(1); // create the bigInt with value 1.

foreach (var line in lines) // iterate through lines
{
    big *= Convert.ToInt32(line); // Multiply bigInt with each line.
}

string outputFilename = @"C:\output.txt"; // put the full output file path and name here

File.WriteAllText(outputFilename, big.ToString()); // write the result into text file

This may take a long time to complete. but this all depends on hardware that is operating. You may get memory overflow exception during this task which depends on amount of memory you have.