Tech Jargon - Decoded

Sieve of Eratosthenes

public class Sieve {
 public static boolean[] sieve(int n) {
 boolean[] isPrime = new boolean[n + 1];
 for (int i = 2; i <= n; i++) {
 isPrime[i] = true;
 }
 for (int p = 2; p * p <= n; p++) {
 if (isPrime[p]) {
 for (int i = p * p; i <= n; i += p) {
 isPrime[i] = false;
 }
 }
 }
 return isPrime;
 }

 public static void main(String[] args) {
 boolean[] primes = sieve(30);
 for (int i = 2; i < primes.length; i++) {
 if (primes[i]) {
 System.out.print(i + " ");
 }
 }
 System.out.println();
 }
}

#Java #Factorial #TrailingZeros

Count Trailing Zeros in Factorial

public class TrailingZeros {

    public static int countTrailingZeros(int n) {
        int count = 0;
        for (int i = 5; n / i >= 1; i *= 5) {
            count += n / i;
        }
        return count;
    }

    public static void main(String[] args) {
        int number = 25;
        int zeros = countTrailingZeros(number);
        System.out.println("Trailing zeros in " + number + "! is: " + zeros);
    }
}

#Java #Bitwise #Interview

Check if Number is Power of 2

public class PowerOfTwo {
    public static boolean isPowerOfTwo(int n) {
        if (n <= 0) {
            return false;
        }
        return (n & (n - 1)) == 0;
    }

    public static void main(String[] args) {
        System.out.println(isPowerOfTwo(16));
        System.out.println(isPowerOfTwo(15));
        System.out.println(isPowerOfTwo(0));
    }
}

#Java #Interview #Divisors

Print All Divisors of a Number

public class Divisors {

    public static void printDivisors(int n) {
        for (int i = 1; i <= Math.sqrt(n); i++) {
            if (n % i == 0) {
                if (n / i == i) {
                    System.out.print(i + " ");
                } else {
                    System.out.print(i + " " + n/i + " ");
                }
            }
        }
        System.out.println();
    }

    public static void main(String[] args) {
        int num = 36;
        System.out.print("Divisors of " + num + " are: ");
        printDivisors(num);
    }
}

#Java #NeonNumber

Check Neon Number

public class NeonNumber {

    public static boolean isNeon(int number) {
        int square = number * number;
        int sum = 0;
        while (square > 0) {
            int digit = square % 10;
            sum += digit;
            square /= 10;
        }
        return sum == number;
    }

    public static void main(String[] args) {
        int num = 9;
        if (isNeon(num)) {
            System.out.println(num + " is a Neon number.");
        } else {
            System.out.println(num + " is not a Neon number.");
        }
    }
}

#Java #Recursion

Check Magic Number

public class MagicNumberChecker {

    public static boolean isMagicNumber(int num) {
        if (num < 10) {
            return num == 1;
        }

        int sum = 0;
        while (num > 0) {
            sum += num % 10;
            num /= 10;
        }

        return isMagicNumber(sum);
    }

    public static void main(String[] args) {
        System.out.println(isMagicNumber(19));
        System.out.println(isMagicNumber(1234));
        System.out.println(isMagicNumber(1));
    }
}

#Java #AutomorphicNumber

Check Automorphic Number

public class Automorphic {

    public static boolean isAutomorphic(int num) {
        int square = num * num;
        String numStr = String.valueOf(num);
        String squareStr = String.valueOf(square);
        return squareStr.endsWith(numStr);
    }

    public static void main(String[] args) {
        int number = 76;
        if (isAutomorphic(number)) {
            System.out.println(number + " is an automorphic number.");
        } else {
            System.out.println(number + " is not an automorphic number.");
        }
    }
}

#Java #NumberTheory

Check Harshad (Niven) Number

public class HarshadNumber {
    public static boolean isHarshad(int number) {
        if (number <= 0) {
            return false;
        }
        int sum = 0;
        int temp = number;
        while (temp > 0) {
            sum += temp % 10;
            temp /= 10;
        }
        return number % sum == 0;
    }

    public static void main(String[] args) {
        int num = 171;
        if (isHarshad(num)) {
            System.out.println(num + " is a Harshad number.");
        } else {
            System.out.println(num + " is not a Harshad number.");
        }
    }
}

#Java #GCDLCM

GCD & LCM of Two Numbers

public class GCDLCM {
    public static int gcd(int a, int b) {
        if (b == 0) {
            return a;
        }
        return gcd(b, a % b);
    }

    public static int lcm(int a, int b) {
        return (a * b) / gcd(a, b);
    }

    public static void main(String[] args) {
        int num1 = 12;
        int num2 = 18;
        System.out.println("GCD of " + num1 + " and " + num2 + " is: " + gcd(num1, num2));
        System.out.println("LCM of " + num1 + " and " + num2 + " is: " + lcm(num1, num2));
    }
}

#Java #NumberTheory

Check Strong Number

public class StrongNumber {

    public static boolean isStrong(int num) {
        int sum = 0;
        int temp = num;
        while (temp > 0) {
            int digit = temp % 10;
            sum += factorial(digit);
            temp /= 10;
        }
        return sum == num;
    }

    private static int factorial(int n) {
        if (n == 0)
            return 1;
        int fact = 1;
        for (int i = 1; i <= n; i++) {
            fact *= i;
        }
        return fact;
    }

    public static void main(String[] args) {
        int number = 145;
        if (isStrong(number)) {
            System.out.println(number + " is a strong number");
        } else {
            System.out.println(number + " is not a strong number");
        }
    }
}

#Java #PerfectNumber #CodingInterview