How to encode a decimal number to binary in 16 bits in C#?-CodePudding

The problem is asking :

The user gives me integer n,

I convert it to binary in 16 bits,

inverse the binary,

then decode the inverse binary into a new integer.

example:

14769 is 0011100110110001 (the 2 zeros in the front are the problem for me)

inverse the binary:

1000110110011100

Decode:

36252

I wrote the code but when I convert to binary it only gives me 11100110110001 without 00 in front, so the whole inverse binary will change and the new integer will be different.

This is my code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace HelloWorld
{
  public class Program
  {
  public static void Main(string[] args)
  {
    long n, n1, p, i, r, sum, inv, inv1, newint;
    Console.WriteLine("give n:");
    n=long.Parse(Console.ReadLine());
    n1=n;
    p=1;
    sum=0;
    i=n;
    //for below is for the binary representation of n
    for(i=n;i!=0;i=i/2)
    {
      r=i%2;
      sum=sum r*p;
      p=p*10;        
   }

   inv=0;
   //for below is to inverse the above binary representation 
   for(i=sum;i!=0;i=i/10) 
   {
     r=i;
     inv=10*inv r;       
   }

   inv1=inv;
   newint=0;
   p=0;
   //for below is to decode the inverse binary to its decimal representation 
   for(i=inv;i!=0;i=i/10)
   {
     r=i;
     newint=newint r*(long)Math.Pow(2,p);
     p=p 1;
   }
   Console.WriteLine("The number that you gave = {0} \nIts binary 
   representation = {1} \n\nThe inverse binary representation = {2} \nThe integer corresponding to the inverse binary number = {3}", n1, sum, inv1, newint); 
   } 
 }
 }

So how can i encode on 16 bits?

Edit:

1)We didn't learn built in functions

2)We didn't learn padding or Convert.Int...

3)We only know the for loop ( while loop but better not use it)

4)We can't use strings either

CodePudding user response：

You can try using Convert to obtain binary representation and Aggregate (Linq) to get back decimal:

using System.Linq;
...

int value = 14769;
      
int result = Convert
  .ToString(value, 2) // Binary representation
  .PadLeft(16, '0')   // Ensure it is 16 characters long
  .Reverse()          // Reverse
  .Aggregate(0, (s, a) => s * 2   a - '0'); // Back to decimal

Console.Write($"{value} => {result}");

Output:

14769 => 36252

Edit: Loop solution (if you are not allowed to use the classes above...)

int value = 14769;
int result = 0;

for (int i = 0, v = value; i < 16;   i, v /= 2)
  result = result * 2   v % 2;

Console.Write($"{value} => {result}");

CodePudding user response：

You could reverse the bits using some simple bitwise operators.

ushort num = 14769;
ushort result = 0;

// ushort is 16 bits, therefore exactly 16 iterations is required    
for (var i = 0; i < 16; i  , num >>= 1){
    // shift result bits left by 1 position
    result <<= 1;

    // add the i'th bit in the first position
    result |= (ushort)(num & 1);
}

Console.WriteLine(result); //36252