Given a Binary Number as Input. Now, write a Kotlin Program to Convert Binary Number to equivalent decimal number.

Input:
100

Output:
4

Input:
110

Output:
6

Input:
101

Output:
5

1. Program to Convert Binary to Decimal

Pseudo Algorithm

• Initialise a variable decimalNum, that stores equivalent decimal value, with 0
• Extract each digit from the given binary number.
• While extracting, multiply the extracted digit with proper base (power of 2).
• For example, if binary number is 110, decimalNum = 1 * (2^2) + 1 * (2^1) + 0 * (2^0) = 6

Sourcecode –

import java.util.*

fun main() {
    val read = Scanner(System.`in`)

    println("Enter n:")
    val binaryN = read.nextLong()

    var decimalNum: Long = 0
    if(checkBinary(binaryN)) {
        var n = binaryN

        var base = 1
        while (n != 0.toLong()) {
            val lastDigit = n % 10
            n /= 10
            decimalNum += lastDigit * base
            base *= 2
        }
        println("Equivalent Decimal : $decimalNum")
    } else {
        println("$binaryN is not a binary number")
    }
}

private fun checkBinary(binaryNum: Long): Boolean {
    var isBinary = true

    var n = binaryNum
    while (n != 0.toLong()) {
        val lastDigit = n % 10
        if(!((lastDigit == 0.toLong()) || (lastDigit == 1.toLong()))) {
                isBinary = false
                break
            }
        n /= 10
    }
    return isBinary
}

When you run the program, output will be –

Enter n:
100010
Equivalent Decimal : 34

Explanation:

Here, we have created an object of Scanner. Scanner takes an argument which says where to take input from.
System.`in` means take input from standard input – Keyboard.

read.nextLong() means read anything entered by user before space or line break from standard input – Keyboard.

We stored value entered by user in variable binaryN.

At first, we checked if entered value is binary or not.
If NO, we print a message ” number is not binary number”.

• We use checkBinary function to check if number is binary or not. If any digit in number is neither 0 nor 1, then, it is not binary number.

If Yes, we start converting those number into decimal –

• variable base contains power of 2 to the position at which current last digit we have in lastDigit
• Decimal value is sum of lastDigit * (power of 2 to the position at which current lastDigit is at)
• For example,
  binaryN = 110

  decimalN = 1 * (2 ^ 2) + 1 * (2^1) + 1 * (2 ^ 0) = 6

Thus, we went through Kotlin program to convert binary number to equivalent decimal number.