Flatten Binary Tree to Linked List.java

Flatten Binary Tree to Linked ListOct 14 '12
Given a binary tree, flatten it to a linked list in-place.

For example,
Given

         1
        / \
       2   5
      / \   \
     3   4   6
The flattened tree should look like:
   1
    \
     2
      \
       3
        \
         4
          \
           5
            \
             6

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public void flatten(TreeNode root) {
    	if (root == null || (root.left == null && root.right == null)) return;
	if (root.left != null) {
	    TreeNode tmp = root.right;
	    root.right = root.left;
	    root.left = null;
	    TreeNode rightMost = findRightMostNode(root.right);
	    rightMost.right = tmp;
	    flatten(root.right);
	} else if (root.right != null) {
	    flatten(root.right);
	}
    }
	
    public TreeNode findRightMostNode(TreeNode root) {
	if (root.right != null) {
	    return findRightMostNode(root.right);
	} else {
	    return root;
	}
    }
}