make expression from numbers

[Pavle]

How to make that computer makes expression from given random numbers to calculate given three-digit number ,if he can't get that number he should calculate closest to him?
In first three labels is random generated three-digit number,in second four labels are random generated numbers can be from 1 to 9,in third label random generated numbers can be(10,15 or 20) in fourth label random generated numbers can be (25,50,75 or 100).

 

[jmcilhinney]

That's a rather confusing explanation. Maybe an example is in order.

 

[Pavle]

For example random number to be found is 435 and numbers available to found that number are:
6, 9, 3, 8, 15, 100


Computer should find it like this: 435 = (9 + (3 * (100 + (6 * (15 - 8))))) and show that steps in textbox


Or for example random number to be found is 945 and numbers available to found that number are:
3,2,1,2,10,25 computer can't find that number but he can find closest to that number:
944=2*(25*(2*10-1)-3) and show that steps in textbox

 

[jmcilhinney]

That's far from trivial. What efforts have you made on your own behalf? As I often say, the way to solve a programming problem is to first forget that it's a programming problem. Let's say that you had to do this manually with pen and paper. How would you do it? There's no programming involved so a lack of programming experience is neither reason nor excuse for not being able to at least make an effort. Once you have a solution, write it out as a series of steps. That will be your algorithm. The programming part of the problem is then simply to write code to implement that algorithm. We can certainly help you with that but, if you don't already have an algorithm, you haven't tried hard enough.

 

[Pavle]

Here is the code,but how to not use all values to make expression and how to if computer cannot find target number to make expression for closest to target value?

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


namespace Expression_Evaluator
{
    class Program
    {


           static int[] ReadInput(out int value)
        {
            Console.Write("Enter integer numbers to use (space-separated): ");
            string s = Console.ReadLine();
            string[] parts = s.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);


            int[] a = new int[parts.Length];
            for (int i = 0; i < a.Length; i++)
                a[i] = int.Parse(parts[i]);


            Console.Write("Enter integer value to calculate: ");
            value = int.Parse(Console.ReadLine());


            return a;


        }
        static void SolveAndPrint(int[] numbers, int targetValue)
        {


            int targetKey = (targetValue << numbers.Length) + (1 << numbers.Length) - 1;


            HashSet<int> solvedKeys = new HashSet<int>();
            Dictionary<int, int> keyToLeftParent = new Dictionary<int, int>();
            Dictionary<int, int> keyToRightParent = new Dictionary<int, int>();
            Dictionary<int, char> keyToOperator = new Dictionary<int, char>();
            Queue<int> queue = new Queue<int>();


            for (int i = 0; i < numbers.Length; i++)
            {
                
                int key = (numbers[i] << numbers.Length) + (1 << i);


                solvedKeys.Add(key);
                queue.Enqueue(key);


            }


            while (queue.Count > 0 && !solvedKeys.Contains(targetKey))
            {


                int curKey = queue.Dequeue();


                int curMask = curKey & ((1 << numbers.Length) - 1);
                int curValue = curKey >> numbers.Length;


                int[] keys = new int[solvedKeys.Count];
                solvedKeys.CopyTo(keys);


                for (int i = 0; i < keys.Length; i++)
                {
                    
                    int mask = keys[i] & ((1 << numbers.Length) - 1);
                    int value = keys[i] >> numbers.Length;


                    if ((mask & curMask) == 0)
                    {
                        for (int op = 0; op < 6; op++)
                        {


                            char opSign = '\0';
                            int newValue = 0;


                            switch (op)
                            {
                                case 0: // Addition
                                    newValue = curValue + value;
                                    opSign = '+';
                                    break;
                                case 1: // Subtraction - another value subtracted from current
                                    newValue = curValue - value;
                                    opSign = '-';
                                    break;
                                case 2: // Subtraction - current value subtracted from another
                                    newValue = value - curValue;
                                    opSign = '-';
                                    break;
                                case 3: // Multiplication
                                    newValue = curValue * value;
                                    opSign = '*';
                                    break;
                                case 4: // Division - current divided by another
                                    newValue = -1;  // Indicates failure to divide
                                    if (value != 0 && curValue % value == 0)
                                        newValue = curValue / value;
                                    opSign = ' ';
                                    break;
                                case 5: // Division - other value divided by current
                                    newValue = -1;  // Indicates failure to divide
                                    if (curValue != 0 && value % curValue == 0)
                                        newValue = value / curValue;
                                    opSign = ' ';
                                    break;
                            }


                            if (newValue >= 0)
                            {   
                                int newMask = (curMask | mask);
                                
                                int newKey = (newValue << numbers.Length) + newMask;


                                if (!solvedKeys.Contains(newKey))
                                {    
                                    solvedKeys.Add(newKey);
                                    
                                    if (op == 2 || op == 5)
                                    {   
                                        keyToLeftParent.Add(newKey, keys[i]);
                                        keyToRightParent.Add(newKey, curKey);
                                    }
                                    else
                                    {
                                        keyToLeftParent.Add(newKey, curKey);
                                        keyToRightParent.Add(newKey, keys[i]);
                                    }


                                    keyToOperator.Add(newKey, opSign);
                                    solvedKeys.Add(newKey);
                                    queue.Enqueue(newKey);
                                    
                                }


                            }


                        }
                    }
                }


            }


            if (!solvedKeys.Contains(targetKey))
                Console.WriteLine("Solution has not been found.");
            else
            {
                PrintExpression(keyToLeftParent, keyToRightParent, keyToOperator, targetKey, numbers.Length);
                Console.WriteLine("={0}", targetValue);
            }
        }


        static void PrintExpression(Dictionary<int, int> keyToLeftParent, Dictionary<int, int> keyToRightParent, Dictionary<int, char> keyToOperator,
                                    int key, int numbersCount)
        {
            if (!keyToOperator.ContainsKey(key))
                Console.Write("{0}", key >> numbersCount);
            else
            {
                Console.Write("(");


                PrintExpression(keyToLeftParent, keyToRightParent, keyToOperator,
                                keyToLeftParent[key], numbersCount);


                Console.Write(keyToOperator[key]);


                PrintExpression(keyToLeftParent, keyToRightParent, keyToOperator,
                                keyToRightParent[key], numbersCount);
                Console.Write(")");
            }
        }
       static void Main(string[] args)
        {
            while (true)
            {


                int value;
                int[] numbers = ReadInput(out value);


                SolveAndPrint(numbers, value);


                Console.Write("More? (y/n) ");
                if (Console.ReadLine().ToLower() != "y")
                    break;


            }
        }
    }
}