C#•2y ago

❔ How to generate all possible multiplications of a given number?

I have this code:

using System;

class GFG
{

   
   static void findCombinationsUtil(int[] arr, int index, int num, int reducedNum)
    {
        
        if (reducedNum < 0)
            return;

       
        if (reducedNum == 0)
        {
            for (int i = 0; i < index; i++)
                Console.Write(arr[i] + " ");
            Console.WriteLine();
            return;
        }

        
        int prev = (index == 0) ?
                              1 : arr[index - 1];

       
        for (int k = prev; k <= num; k++)
        {
           
            arr[index] = k;

           
            findCombinationsUtil(arr, index + 1, num, reducedNum - k);
        }
    }

    
    static void findCombinations(int n)
    {
      
        int[] arr = new int[n];

      
        findCombinationsUtil(arr, 0, n, n);
    }

    
    static public void Main()
    {
       
        Console.WriteLine("Enter number: ");
        int n = Convert.ToInt32(Console.ReadLine());
        Console.WriteLine("Disintegration is: " + n);
        findCombinations(n);
    }
}

using System;

class GFG
{

   
   static void findCombinationsUtil(int[] arr, int index, int num, int reducedNum)
    {
        
        if (reducedNum < 0)
            return;

       
        if (reducedNum == 0)
        {
            for (int i = 0; i < index; i++)
                Console.Write(arr[i] + " ");
            Console.WriteLine();
            return;
        }

        
        int prev = (index == 0) ?
                              1 : arr[index - 1];

       
        for (int k = prev; k <= num; k++)
        {
           
            arr[index] = k;

           
            findCombinationsUtil(arr, index + 1, num, reducedNum - k);
        }
    }

    
    static void findCombinations(int n)
    {
      
        int[] arr = new int[n];

      
        findCombinationsUtil(arr, 0, n, n);
    }

    
    static public void Main()
    {
       
        Console.WriteLine("Enter number: ");
        int n = Convert.ToInt32(Console.ReadLine());
        Console.WriteLine("Disintegration is: " + n);
        findCombinations(n);
    }
}

And what it does is it generates all the sums of a given number. Here's how it works: Input: 3 Output: 1 1 1 2 1 So I enter any number I want and it generates all possible sums of that number. I want to do the same but with multiplications. Anyone know how?

24 Replies

NameOP•2y ago

for example: if I enter 10, I want to get 5x2, 10x1 same as the program I already have but with multiplication

Cattywampus•2y ago

this should do it

        int input = 12;
        int a = 0; int b = 0;
        
        while(a != input)
        {
            var mul = a * b;
            
            if(mul == input)
            {
                Console.WriteLine(a + " x " + b);
            }
            
            if(b == input)
            {
                b = 0;
                a++;
            }
            else
            {
                b++;
            }
        }

        int input = 12;
        int a = 0; int b = 0;
        
        while(a != input)
        {
            var mul = a * b;
            
            if(mul == input)
            {
                Console.WriteLine(a + " x " + b);
            }
            
            if(b == input)
            {
                b = 0;
                a++;
            }
            else
            {
                b++;
            }
        }

(I don't know how to compile it here, don't know the command, really ) 2d array should be more appropriate here, but eh.. btw, a simple and fun question... I like it 😻

MODiX•2y ago

To compile C# code in Discord, use !eval Example:

!eval for(int i = 0; i < 4; i++) Console.WriteLine(i);

!eval for(int i = 0; i < 4; i++) Console.WriteLine(i);

Please don't try breaking the REPL service. Also, remember to do so in #bot-spam!

MODiX•2y ago

SlimStv#2835

REPL Result: Success

int input = 12;
        int a = 0; int b = 0;
        
        while(a != input)
        {
            var mul = a * b;
            
            if(mul == input)
            {
                Console.WriteLine(a + " x " + b);
            }
            
            if(b == input)
            {
                b = 0;
                a++;
            }
            else
            {
                b++;
            }
        }

int input = 12;
        int a = 0; int b = 0;
        
        while(a != input)
        {
            var mul = a * b;
            
            if(mul == input)
            {
                Console.WriteLine(a + " x " + b);
            }
            
            if(b == input)
            {
                b = 0;
                a++;
            }
            else
            {
                b++;
            }
        }

Console Output

Compile: 631.433ms | Execution: 54.071ms | React with ❌ to remove this embed.

Cattywampus•2y ago

I typed this directly on my browser catfine

(also notice a bug there?) I'll fix it later when I get back to my desk

MODiX•2y ago

SlimStv#2835

REPL Result: Success

int input = 12;
        int a = 0; int b = 0;
        
        while(a <= input)
        {
            var mul = a * b;
            
            if(mul == input)
            {
                Console.WriteLine(a + " x " + b);
            }
            
            if(b == input)
            {
                b = 0;
                a++;
            }
            else
            {
                b++;
            }
        }

int input = 12;
        int a = 0; int b = 0;
        
        while(a <= input)
        {
            var mul = a * b;
            
            if(mul == input)
            {
                Console.WriteLine(a + " x " + b);
            }
            
            if(b == input)
            {
                b = 0;
                a++;
            }
            else
            {
                b++;
            }
        }

Console Output

Compile: 592.952ms | Execution: 96.014ms | React with ❌ to remove this embed.

NameOP•2y ago

yes. That is what I want but with one small detail: the input must be entered by the user

Cattywampus•2y ago

well yeah? just replace the input with whatever you want there Do your best 1st and if you're stuck post it here, being spoonfed would not help you learn the language

NameOP•2y ago

I meant, entered in the console

NameOP•2y ago

ok, I will try it nice, it works! 1x12 and 12x1 is the same. What should I do if I don't want any repetition?

Cattywampus•2y ago

hi, sorry was busy with irl stuff.. bcos we're comparing 2 values of the same range, so once the value of a bigger than the value of b you'd need to break out of the loop so the repetition won't happen. It's a simple math

MODiX•2y ago

SlimStv#2835

REPL Result: Success

int input = 8;
        int a = 0; int b = 0;
        
        while(a <= input)
        {
            var mul = a * b;
            
            if(mul == input)
            {
                if(a > b)
                    break;
                
                Console.WriteLine(a + " x " + b);
            }
            
            if(b == input)
            {
                b = 0;
                a++;
            }
            else
            {
                b++;
            }
        }

int input = 8;
        int a = 0; int b = 0;
        
        while(a <= input)
        {
            var mul = a * b;
            
            if(mul == input)
            {
                if(a > b)
                    break;
                
                Console.WriteLine(a + " x " + b);
            }
            
            if(b == input)
            {
                b = 0;
                a++;
            }
            else
            {
                b++;
            }
        }

Console Output

1 x 8
2 x 4

1 x 8
2 x 4

Compile: 624.065ms | Execution: 114.532ms | React with ❌ to remove this embed.

MODiX•2y ago

SlimStv#2835

REPL Result: Success

int input = 20;
        int a = 0; int b = 0;
        
        while(a <= input)
        {
            var mul = a * b;
            
            if(mul == input)
            {
                if(a > b)
                    break;
                
                Console.WriteLine(a + " x " + b);
            }
            
            if(b == input)
            {
                b = 0;
                a++;
            }
            else
            {
                b++;
            }
        }

int input = 20;
        int a = 0; int b = 0;
        
        while(a <= input)
        {
            var mul = a * b;
            
            if(mul == input)
            {
                if(a > b)
                    break;
                
                Console.WriteLine(a + " x " + b);
            }
            
            if(b == input)
            {
                b = 0;
                a++;
            }
            else
            {
                b++;
            }
        }

Console Output

1 x 20
2 x 10
4 x 5

1 x 20
2 x 10
4 x 5

Compile: 625.256ms | Execution: 91.037ms | React with ❌ to remove this embed.

Cattywampus•2y ago

@Name

NameOP•2y ago

Ah Thank you very much! It looks good

Cattywampus•2y ago

goodluck!

Anton•2y ago

The best way is to break down the number into its prime factorization, like 72 = 2 × 2 × 2 × 3 × 3 = 2^3 × 3^2 And then go through all combinations of these: (2^0 × 3^0) × (2^3 × 3^2) = 1 × 72 (2^1 × 3^0) × (2^2 × 3^2) = 2 × 36 (2^2 × 3^0) × (2^1 × 3^2) = 4 × 18 (2^3 × 3^0) × (2^0 × 3^2) = 8 × 9 (2^0 × 3^1) × (2^3 × 3^1) = 3 × 24 (2^1 × 3^1) × (2^2 × 3^1) = 6 × 12 After that the combinations repeat in the previous products.

Cattywampus•2y ago

too complicated, no? 😃 its a comparison of same length, so once b > a it will be guaranteed that repetition will occur

Anton•2y ago

Sure, it'll require more logic. But basing your solution on that principle is required for being able to produce the fastest possible code for larger numbers

Cattywampus•2y ago

so you only need to calc half of a and forget the rest

Anton•2y ago

you end up doing more operations in your solution, which is fine for small numbers I'm talking theoretically rn

Cattywampus•2y ago

that was a leftover from 1st solution... it can be much less code for sure with his updated question and the a > b can be eliminated entirely also yeah, I should've updated it rather than copy pasting previous answer when

Anton•2y ago

it doesn't matter really what you do to your code, it won't become optimal. It will have larger complexity than if you used the principal I stated above your current solution is O(N) ah no O(N^2) because there are two variables that you increment until you number (or half your number) sieve of Eratosthenes has better complexity

Accord•2y 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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❔ How to generate all possible multiplications of a given number?