day1: add basic dsa code

Basic/Armstrong.java

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+// write code to check armstrong number
+
+import java.util.Scanner;
+
+class Armstrong{
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+        System.out.println("Enter a number to check if it is an Armstrong number or not");
+        int num = scanner.nextInt();
+        scanner.close();
+        int temp = num;
+        int sum = 0;
+        while(num>0){
+            int rem = num%10;
+            sum += rem*rem*rem;
+            num = num/10;
+        }
+        if(sum == temp){
+            System.out.println("The number is an Armstrong number");
+        }
+        else{
+            System.out.println("The number is not an Armstrong number");
+        }
+    }
+}

Basic/CheckPallindrome.java

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+// write a code in java to check palindrome number
+
+import java.util.Scanner;
+class CheckPalindrome{
+    public static void main(String args[]){
+        int n, sum = 0, r, temp;
+        Scanner scanner = new Scanner(System.in);
+        System.out.print("Enter a number:");
+        n = scanner.nextInt();
+        scanner.close();
+        temp = n;
+        while(n > 0)
+        {
+            r = n % 10;
+            sum = (sum*10) + r;
+            n = n/10;
+        }
+        if(temp == sum)
+        {
+            System.out.println("Given number is Palindrome");
+        }
+        else
+        {
+            System.out.println("Given number is not Palindrome");
+        }
+    }
+}

Basic/CheckPrime.java

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+// write a code in java to check for prime numbers in o(n^1/2) time complexity using function
+
+import java.util.Scanner;
+
+class CheckPrime {
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+        System.out.println("Enter a number to check if it is prime or not: ");
+        int num = scanner.nextInt();
+        scanner.close();
+        if (isPrime(num)) {
+            System.out.println(num + " is a prime number");
+        } else {
+            System.out.println(num + " is not a prime number");
+        }
+    }
+
+    static boolean isPrime(int num) {
+        if (num <= 1) {
+            return false;
+        }
+        for (int i = 2; i * i <= num; i++) {
+            if (num % i == 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+}

Basic/PrintAllDivisors.java

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+// write a code in java to print all divisors in o(n ^ 1/2) time complexity using function
+
+import java.util.Scanner;
+
+class PrintAllDivisors{
+    public static void main(String[] args){
+        Scanner scanner = new Scanner(System.in);
+        int n = scanner.nextInt();
+        scanner.close();
+        printDivisors(n);
+    }
+
+    static void printDivisors(int n){
+        for(int i = 1; i * i <= n; i++){
+            if(n % i == 0){
+                System.out.print(i + " ");
+                if(i != n / i){
+                    System.out.print(n / i + " ");
+                }
+            }
+        }
+    }
+}

Basic/ReverseNumber.java

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+// write a code to reverse a number in java 
+// input: 1234
+// output: 4321
+
+import java.util.Scanner;
+
+class ReverseNumber {
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+        System.out.println("Enter a number: ");
+        int num = scanner.nextInt();
+        scanner.close();
+        int rev = 0;
+        while (num != 0) {
+            int digit = num % 10;
+            rev = rev * 10 + digit;
+            num = num / 10;
+        }
+        System.out.println("Reversed number: " + rev);
+    }
+}

Basic/gcdORhcf.java

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+// write a code to find gcd using euclidean algorithm in a function
+
+import java.util.Scanner;
+
+class gcdORhcf {
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+        System.out.println("Enter two numbers to find their GCD: ");
+        int num1 = scanner.nextInt();
+        int num2 = scanner.nextInt();
+        scanner.close();
+        System.out.println("GCD of " + num1 + " and " + num2 + " is " + findGCD(num1, num2));
+    }
+
+    public static int findGCD(int num1, int num2) {
+        if (num2 == 0) {
+            return num1;
+        }
+        return findGCD(num2, num1 % num2);
+    }
+}