114. Flatten Binary Tree to Linked List

把左边=null, 把最左边遍历到null 保证已经flatten 然后再弄右边 然后把root.right跟左边连接,再把右边连接到root.right的最下面

https://leetcode.com/problems/flatten-binary-tree-to-linked-list/discuss/36987/Straightforward-Java-Solution

 

 

class Solution {
    public void flatten(TreeNode root) {
        if(root == null) return;
        TreeNode left = root.left;
        TreeNode right = root.right;
        root.left = null;
        
        flatten(right);
        flatten(left);
        root.right = left;
        TreeNode cur = root;
        while(cur.right != null) cur = cur.right;
        cur.right = right;
        
    }
}