Flatten 1

Flatten1.java

package com.interviewbytes.trees;

import java.util.LinkedList;
import java.util.List;

public class Flatten1 {

    public void flatten(TreeNode root) {

        List<TreeNode> list = new LinkedList<>();
        dfs(root, list);

        TreeNode current = new TreeNode(0);

        for (TreeNode n : list) {
            current.right = n;
            current.left = null;
            current = current.right;
        }


    }

    private void dfs(TreeNode node, List<TreeNode> list) {
        if (node == null) return;
        list.add(node);
        dfs(node.left, list);
        dfs(node.right, list);
    }

}

TreeNode.java

package com.interviewbytes.trees;

public class TreeNode {

    int val;
    TreeNode left;
    TreeNode right;

    TreeNode(int x) {
        val = x;
    }
}