Merge pull request #3 from souravpalitrana/feature/permutation_alternate

Add the solution of permutation duplicate and also alternate solution

Author: souravpalitrana

Recursion/Permutation/src/permutation/PermutationAlternate.java

@@ -15,13 +15,13 @@ public class PermutationAlternate {
      * @param args the command line arguments
      */
     public static void main(String[] args) {
-        String input = "ABCD";
+        String input = "ABC";
 
         calculate(input, 0, input.length());
     }
 
     public static void calculate(String input, int left, int right) {
-        if (left == right) {
+        if (left == right - 1) {
             System.out.println(input);
         } else {
             for (int i = left; i < right; i++) {

Recursion/Permutation/src/permutation/PermutationWithDuplicateAlternate.java

@@ -0,0 +1,45 @@
+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package permutation;
+
+/**
+ *
+ * @author souravpalit
+ */
+public class PermutationWithDuplicateAlternate {
+
+    /**
+     * @param args the command line arguments
+     */
+    public static void main(String[] args) {
+        String input = "AAB";
+        
+        calculate(input, 0, input.length());
+    }
+    
+    public static void calculate(String input, int left, int right) {
+        if (left == right) {
+            System.out.println(input);
+        } else {
+            for (int i = left; i < right; i++) {
+                if (i != 0 && input.charAt(i) == input.charAt(i -1)) {
+                    continue;
+                } else {
+                    String swapped = swap(input, left, i);
+                    calculate(swapped, left + 1, right);
+                }
+            }
+        }
+    }
+    
+    public static String swap(String input, int first, int second) {
+        char [] inputChars = input.toCharArray();
+        char temp = inputChars[first];
+        inputChars[first] = inputChars[second];
+        inputChars[second] = temp;
+        return String.valueOf(inputChars);
+    }
+}