/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Codec {
    public String serialize(TreeNode root) {
        return rserialize(root, "");
    }
  
    public TreeNode deserialize(String data) {
        String[] dataArray = data.split(",");
        List<String> dataList = new LinkedList<String>(Arrays.asList(dataArray));
        return rdeserialize(dataList);
    }

    public String rserialize(TreeNode root, String str) {
        if (root == null) {
            str += "None,";
        } else {
            str += str.valueOf(root.val) + ",";
            str = rserialize(root.left, str);
            str = rserialize(root.right, str);
        }
        return str;
    }
  
    public TreeNode rdeserialize(List<String> dataList) {
        if (dataList.get(0).equals("None")) {
            dataList.remove(0);
            return null;
        }
  
        TreeNode root = new TreeNode(Integer.valueOf(dataList.get(0)));
        dataList.remove(0);
        root.left = rdeserialize(dataList);
        root.right = rdeserialize(dataList);
    
        return root;
    }
}


// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.deserialize(codec.serialize(root));

class Solution {
    List<String> rec;
    boolean[] vis;

    public String[] permutation(String s) {
        int n = s.length();
        rec = new ArrayList<String>();
        vis = new boolean[n];
        char[] arr = s.toCharArray();
        Arrays.sort(arr);
        StringBuffer perm = new StringBuffer();
        backtrack(arr, 0, n, perm);
        int size = rec.size();
        String[] recArr = new String[size];
        for (int i = 0; i < size; i++) {
            recArr[i] = rec.get(i);
        }
        return recArr;
    }

    public void backtrack(char[] arr, int i, int n, StringBuffer perm) {
        if (i == n) {
            rec.add(perm.toString());
            return;
        }
        for (int j = 0; j < n; j++) {
            if (vis[j] || (j > 0 && !vis[j - 1] && arr[j - 1] == arr[j])) {
                continue;
            }
            vis[j] = true;
            perm.append(arr[j]);
            backtrack(arr, i + 1, n, perm);
            perm.deleteCharAt(perm.length() - 1);
            vis[j] = false;
        }
    }
}