Java Interviews: DSA - Bit Manipulation

Binary Left Shift (Multiplies):

a << b = a * (2^b)

Original : 0 0 0 0 1 0 1 : Int (5) Shift Left: 0 1 0 1 0 0 : Int (20)

if a = 5, b = 2, hence 5 << 2 and 5 * (2 ^ 2) Therefore 20.

Binary Right Shift (Divides):

a << b = a / (2^b)

Original : 0 1 0 1 0 0 : Int (20) Shift Left: 0 0 0 0 1 0 1 : Int (5)

if a = 20, b = 2, hence 20 << 2 and 20 / (2 ^ 2) Therefore 5.

Sample Interview Questions:

1) Odd Even

    if(x&1){
        System.out.println("Odd");
    }
    else{
        System.out.println("Even");
    }

2) Getting the iTH bit

Take a empty bit, and move the 1 to ith location, such that we can perform AND (&) to the n number.

Step 1: Given: n=5, i=2 n in 0 0 0 1 0 1

Step 2: Build a bit, such that it only has 1 in the ith Location using LeftShift.

mask=0 0 0 0 0 0 0 x<<i i.e. 0 0 0 1 0 0

Step 3: Perform AND with n and mask, res = n & mask (this will multiply)