flatten-binary-tree-to-linked-list.java

class Solution {
    TreeNode prev=null;
    public void flatten(TreeNode root) {
         if(root==null)
            return;
        flatten(root.right);//traverse till right most.
        flatten(root.left);//got to left of right most
       root.left=null;//set left as null
        root.right=prev;//set right to previously traversed node
        prev=root;  //set prev to current node.
    }
    
    
}