change

Enigma.java

@@ -0,0 +1,14 @@
+public class Enigma{
+	public static void enigma(int x){
+		if(x == 0){
+			return;
+		}else{
+			enigma(x/2); //recursively calling enigma
+		}
+		System.out.print(x%2);
+	}
+	public static void main(String[] args) {
+		enigma(5);
+		System.out.println("");
+	}
+}

Palindrome.java

@@ -0,0 +1,61 @@
+import java.util.Scanner;
+
+public class Palindrome{
+	public static char first(String s){
+		return s.charAt(0);
+	}
+
+	public static char last(String s){
+		int length = s.length();
+		return s.charAt(length - 1);
+	}
+
+	public static String middle(String s){
+		int length = s.length();
+		return s.substring(1,length - 1);
+	}
+
+	public static boolean isPalindrome(String s)
+    {
+        if(s.length() == 0 || s.length() == 1)
+            return true;//if length =0 OR 1 then it is 
+        if(first(s) == last(s))//check for first and last char of String, if they are same then do the same thing for a substring with first and last char removed. and carry on this until you string completes or condition fails
+            return isPalindrome(middle(s)); //if its not the case than string is not.
+        return false;
+    }
+
+    public static boolean isPalindromeIter(String s){
+    	int length = s.length(); //get the length of the string
+    	int mid = length/2; // get the middle point of the string
+    	if(length == 0 || length == 1) //return if the string is empty or 1 chracter
+    		return true;
+    	for(int i = 0; i < mid; i++){
+    		if (s.charAt(i) != s.charAt(length-i-1)){ //iterate and return if the characters are not matching
+    			return false;
+    		}
+        }
+    return true;
+    }
+
+    public static boolean isPalindromewhile(String s) {
+    	int left  = 0;                 // index of leftmost unchecked char
+    	int right = s.length() -1;  // index of the rightmost
+
+    	while (left < right) {         // continue until they reach center
+    		if (s.charAt(left) != s.charAt(right)) {
+    			return false;          // if chars are different, finished
+    		}
+    		left++;                    // move left index toward the center
+    		right--;                   // move right index toward the center
+    	}
+    return true;                   // if finished, all chars were same
+	}
+
+	public static void main(String[] args) {
+
+	Scanner scan = new Scanner(System.in);
+	String word = scan.nextLine();
+	System.out.println(isPalindromeIter("word"));
+	System.out.println(isPalindromewhile("word"));
+	}
+}

abecedarian.java

@@ -0,0 +1,32 @@
+public class abecedarian {
+        public static boolean isAbecedarian(String s) {
+                int index = 0;
+                char c = 'a'; 
+                while (index < s.length()) {
+                        if (c > s.charAt(index)) {
+                                return false;
+                        }
+                        c = s.charAt(index); 
+                        index = index + 1;
+
+                }
+                return true;
+        }
+
+        public static boolean isAbecedarianrec(String s){
+                char first = s.charAt(0);
+                char second = first ++;
+                System.out.println(first);
+                System.out.println(second);
+                if (s.charAt(0)<second){
+                         return isAbecedarianrec(s);
+                }
+
+                return false;
+        }
+
+        public static void main(String[] args) {
+                //System.out.println(isAbecedarian("abcde"));
+                System.out.println(isAbecedarianrec("abcde"));
+        }
+}

reverseDigit.java

@@ -0,0 +1,11 @@
+class reverseDigit{
+	public static void main(String[] args) {
+		reversedigit(81);
+	}
+	public static void reversedigit(int n){
+		int lastDigit = n%10;
+		int firstDigit = n/10;
+		System.out.print(lastDigit);
+		System.out.println(firstDigit);
+	}
+}