LeetCode: Flatten Binary Tree to Linked List

LeetCode: Flatten Binary Tree to Linked List 

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46

/**
 * Description
 *
 * @author hzhou
 */
public class FlattenBinaryTreeToLinkedList {
    public void flatten(TreeNode root) {
        if (root == null) {
            return;
        }
        Stack<TreeNode> stack = new Stack<TreeNode>();
        TreeNode cursor = new TreeNode(0);
        stack.push(root);
        while (!stack.isEmpty()) {
            cursor.right = stack.pop();
            cursor.left = null;
            cursor = cursor.right;
            if (cursor.right != null) {
                stack.push(cursor.right);
            }
            if (cursor.left != null) {
                cursor.right = cursor.left;
                if (cursor.left.right != null) {
                    stack.push(cursor.left.right);
                }
                if (cursor.left.left != null) {
                    stack.push(cursor.left.left);
                }
                cursor.left = null;
                cursor = cursor.right;
            }
        }
    }
    @Test
    public void test() {
        TreeNode root = new TreeNode(1);
        root.left = new TreeNode(2);
        /*root.right = new TreeNode(5);
        root.left.left = new TreeNode(3);
        root.left.right = new TreeNode(4);
        root.right.right = new TreeNode(6);
        */
        flatten(root);
    }
}