Check Oddity

Check Oddity

Write the precise code to check the number is Odd or not.

Approach#1

Check the module 2 of number is Zero. If it Zero, number is Odd.

public boolean oddOrNot(int num) {

     return num % 2 == 1;

}

Problem: It will not return the correct result for the negative number.

Approach#2

If number is positive/negative, Subtract 2/-2 from number respectively until the number result is Zero or one.

public boolean oddOrNot(intnum) {

     int s = 0;

     if(num>0) {

           s = 2;

     } else {

           s = -2;

     }

     while(num>1) {

           num = num – s;

     }

     if(num==0) {

           return false;

     } else {

           return true;

     }

}

Complexity of given approach is O(num).

Approach#3

Example:Number = 10

Binary representation of 10 = 1010

Binary representation of 1   = 0001

Logical AND of both numbers = 0000.

A number will be Odd iff last bit of binary representation is 1.

public boolean oddOrNot(intnum) {

    return (num & 1) != 0;

}

This is highly optimized code. Since, Arithmetic and Logical operations are much faster compared to division and multiplication.