There is code

DiffiRecursion.java

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+public class DiffiRecursion {
+    public static int first =-1;
+    public static int last =-1;
+    public static boolean [] map = new boolean[26];
+
+
+//     public static void towerOfHanoi(int n, String src,String Helper,String Dest)
+//     {// base case
+//   if(n==1)
+//   {
+//     System.out.println("transfer disk "+ n+" "+ "from"+" "+src +" "+"to"+" "+Dest);
+//     return;
+//   }
+
+//   towerOfHanoi(n-1, src, Dest, Helper);
+//   System.err.println("transfer disk "+ n+" "+ "from"+" "+src +" "+"to"+" "+Dest);
+//   towerOfHanoi(n-1, Helper, src, Dest);
+
+
+//     }
+
+//     public static  void RevStr(String str,int inx)
+//     {//time complexity = O(n)
+//         if(inx==0)
+//         {
+//             System.out.println(str.charAt(inx));
+//             return;
+//         }
+//         System.out.println(str.charAt(inx));
+//         RevStr(str, inx-1);
+//     }
+
+    public static void FindOcurr(String str, int idx, char element)
+    {  if(idx==str.length())
+        {
+            System.out.println(first);
+            System.out.println(last);
+            return;
+        }
+
+      char Currchar = str.charAt(idx);
+      if(Currchar == element)
+      {
+        if(first ==-1)
+        {
+            first = idx;
+        }
+        else{
+            last= idx;
+        }
+      }
+      FindOcurr(str, idx+1, element);
+
+
+    }
+
+    // public static boolean SortedArray(int arr[],int idx)
+    // {  //we are chcking aray is sorted or not
+    //     //time complexity = O(n)
+    //     if(idx==arr.length-1)
+    //     {
+    //         return true;
+    //     }
+    //     if(arr[idx] <arr[idx+1])
+    //    return SortedArray(arr, idx+1);
+    //     else
+    //    return  false;
+
+    // }
+
+//     public static void MovetoEnd(String str, int idx, char element,int count, String newstr)
+//     {//Time complexity = O(n)
+//         if(idx==str.length()){
+//             for(int i=0;i<count;i++)
+//             {
+//                 newstr+= element;
+//             }
+//             System.out.println(newstr);
+//             return;
+//         }
+// char Currchar = str.charAt(idx);
+// if(Currchar==element)
+// {
+//     count++;
+// MovetoEnd(str, idx+1, element, count, newstr);
+
+// }
+// else{
+//     newstr += Currchar;
+//     MovetoEnd(str, idx+1, element, count, newstr);
+// }
+
+//     }
+
+public static void RemoveDup(String str, int idx,  String newstr)
+{//Time complexity = O(n)
+    if(idx==str.length()){
+       System.out.println(newstr);
+        return;
+    }
+char Currchar = str.charAt(idx);
+if(map[Currchar -'a'])
+RemoveDup(str, idx+1, newstr);
+else
+{
+    newstr +=Currchar;
+    map[Currchar -'a']= true;
+    RemoveDup(str, idx+1, newstr);
+}
+
+
+}
+    public static void main(String[] args) {
+        // int n=3;
+        // towerOfHanoi(n, "S", "H", "D");
+
+        // String str ="abcd";
+        // RevStr(str, str.length()-1);
+
+        // String  str = "habiaathcafaio";
+        // FindOcurr(str, 0, 'a');
+
+        // int arr[]= {1,5,10};
+        // System.out.println(SortedArray(arr, 0));
+
+        String str ="abcadd";
+        RemoveDup(str, 0, "");
+
+    }
+
+}