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binary number input

khalid dcu (3)
I am new to C++ language, could any one help me to figure out " how to take binary number as an input, generate partial products by bit-wise multiplication and in last step to add all the partial products to generate final products".
h4ckb0x7 (19)
Homework question?
khalid dcu (3)
what do you mean by homework question?
h4ckb0x7 (19)
It sounds like a homework question, to which I won't just give you the code. However, a google search of bitwise operators in C++ should help.
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int num = 4;
num = num<<1;
std::cout << "Num = " << num;


Num = 8

That should get you started.

Cheers,
Scott
Last edited on
khalid dcu (3)
it is not homework question, i need it to implement Montgomery multiplication algorithm, if i declare int num; can i store binary value in it or i have to declare string for binary numbers???
h4ckb0x7 (19)
Here you go. It validates input and formats the output. It's probably not the most efficient but it does what it needs to.

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#include <iostream>
#include <iomanip>
#include <string>
#include <vector>

void clearScreen();
std::string validateEntry();
std::string decimalToBin(int number);
int binaryToDec(std::string number);

int main()
{
    clearScreen();
    std::cout << "Enter First Binary Number: ";
    std::string binaryString1 = validateEntry();
    int binaryNum1 = binaryToDec(binaryString1);
    std::cout << "Enter Second Binary Number: ";
    std::string binaryString2 = validateEntry();
    int binaryNum2 = binaryToDec(binaryString2);
    
    std::vector<int> partials(binaryString2.length(), 0);
    
    int bitShift = 0;
    int total = 0;
    for (int i = (binaryString2.length() - 1); i >= 0; i--)
    {
        if (binaryString2.compare(i, 1, "1") == 0)
        {
            partials[bitShift] = binaryNum1<<bitShift;
        }
        else
            partials[bitShift] = 0;
        
        total += partials[bitShift];
        bitShift++;
    }
    
    std::string totalStr = decimalToBin(total);
    total = totalStr.length();
    
    clearScreen();
    
    std::cout << std::fixed
              << std::setw(total) << binaryString1 << "\n"
              << std::setw(total) << binaryString2 << "\n";
    
    for (int i = 0; i < total; i++)
        std::cout << "-";
    std::cout << "\n";
    
    int zeroBuf = binaryString1.length() - 1;
    for (int i = 0; i < (binaryString2.length()); i++)
    {
        std::string tempStr = decimalToBin(partials[i]);
        if (tempStr.length() == 1)
        {
            for (int j = 0; j < zeroBuf; j++)
                tempStr += "0";
        }
        
        zeroBuf++;
        
        std::cout << std::fixed << std::setw(total)
                  << tempStr << "\n";
    }
    for (int i = 0; i < total; i++)
        std::cout << "=";
    std::cout << std::fixed << "\n"
              << std::setw(total) << totalStr << "\n\n";
}

void clearScreen()
{
    std::cout << "\033[2J\033[1;1H";
}

std::string validateEntry()
{
    bool valid = true;
    std::string tempStr;
    
    do
    {
        valid = true;
        getline(std::cin, tempStr);
        for (int i = 0; i < tempStr.length(); i++)
        {
            if ((tempStr.compare(i, 1, "0") != 0) && (tempStr.compare(i, 1, "1") != 0))
            {
                valid = false;
                clearScreen();
                std::cout << "Enter Valid Binary Number: ";
                break;
            }
        }
    } while (valid == false);
    
    clearScreen();
    return tempStr;
}

std::string decimalToBin(int number)
{
    if ( number == 0 ) return "0";
    if ( number == 1 ) return "1";
    
    if ( number % 2 == 0 )
        return decimalToBin(number / 2) + "0";
    else
        return decimalToBin(number / 2) + "1";
}

int binaryToDec(std::string number)
{
    int result = 0, pow = 1;
    for ( int i = number.length() - 1; i >= 0; --i, pow <<= 1 )
        result += (number[i] - '0') * pow;
    
    return result;
}
Last edited on
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