Find the median of n values given by the user without using arrays or any function that uses arrays or any other collection

Question

Only manual algorithms on variables are allowed. Collections like list, arrays etc. aren't to be used. (I Used .length() function in the program but it can be manually done by putting a space after every input and counting the number of chars till a space is found)

Answer 1

The problem that using arrays would solve is to store any number of values that the user inputs. This can be solved by storing the values in a string. Since we'd have to know how many characters to pick from the string to form a number, I've also stored the lengths of the numbers in a separate string(Length would generally be of only 1 digit so we'd know for sure that the length of nth number would be at the nth char in the lengthstorage string.)

The algorithm:

1. Take a number from the string and subtract it from every other number in the string.
2. If the result is positive, add 1 to the int 'pos'; if negative, to 'neg'; if zero, to 'copy'.
3. If odd number of numbers are inputed, then the number for which pos + copy >= n/2 and neg + copy >= n/2 is the median.
4. If even number of numbers are inputed, then we'd have 2 middle numbers fmedian and smedian whose average would be the median. (Refer the code for algorithm).

import java.util.Scanner;
class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    String input,inputstorage,lengthstorage,inputlength;
    int nonrep=0;
    System.out.println("Enter the number of values");
    int n = sc.nextInt();
    int fmedian=0,smedian=0;
    System.out.println("Enter a value");
    input= sc.next();                                                                 //String
    inputlength = "" + (char)(input.length()+48);
    inputstorage = input;
    lengthstorage = inputlength;
    for (int i=1; i<n; i++)
    {
        System.out.println("Enter a value");
        input = sc.next(); 
        inputstorage = inputstorage + input;
        lengthstorage = lengthstorage + (char)(input.length()+48); 
    }                

    int mainnumpos = 0;

    for(int j=0;j<n;j++)
    {
      int copy=0;
      int mainnumlength = lengthstorage.charAt(j) - 48;
        int neg=0,pos=0;
        int mainnum = 0; int factor = 1;int mainnumsign = 0;
        for (int m =mainnumlength-1; m >= 0; m--)
        {
        if(inputstorage.charAt(mainnumpos+m)=='-')
        {
          mainnumsign = 1;
        }
        else
        {
        mainnum += (inputstorage.charAt(mainnumpos+m) - '0') * factor;
        factor *= 10;
        }
        }
        mainnumpos = mainnumpos + mainnumlength;
        if(mainnumsign==1)
        {
          mainnum = -mainnum;
        }

        int position = 0;
        for (int q=0;q<n;q++)

      { int fnumsign = 0;


      int fnumlength = lengthstorage.charAt(q) - 48;

        int fnum = 0;
        factor = 1;
        for (int l =fnumlength-1; l >= 0; l--)
        {
          if(inputstorage.charAt(position+l)=='-')
          {
            fnumsign = 1;
          }
          else{
        fnum += (inputstorage.charAt(position+l) - '0') * factor;
        factor *= 10;
          }
        }
        if(fnumsign==1)
        {
          fnum = -fnum;
        }
        if((mainnum-fnum)>0)
        {
          pos++;
        }
        else if((mainnum-fnum)<0)
        {
          neg++;
        }
        else{
          copy++;
            }
        position = position + fnumlength;



      }

      if((n%2)!=0){

     if((double)(pos+copy)>=((double)n)/2.0 && (double)(neg+copy)>=((double)n)/2.0)
     {
       if(nonrep==0)
       {
       System.out.println("The median is: "+ mainnum);
       nonrep++;
       }                           
     }
     }
     else
     {
       if ((double)(pos+copy)==(double)n/2.0) 
       {
         fmedian=mainnum;
       }
       else if((double)(neg+copy)==(double)n/2.0) 
       {
         smedian = mainnum;
       }
       else if((double)(pos+copy)>=(double)n/2.0 && (double)(neg+copy)>=(double)n/2.0  ) 
       {
         fmedian = mainnum;
         smedian = mainnum;
       }
       if(j==n-1){
         double evenmedian = ((double)(smedian + fmedian))/2.0;
       System.out.println("The median is: "+evenmedian);
       }
     }
    }

  }
}