LeetCode 114. 二叉树展开为链表

114. 二叉树展开为链表

解题思路

1. 先序遍历获取二叉树所有节点的值
2. 构造链表

参考代码

class Solution {
    public void flatten(TreeNode root) {
        if(root == null) {
            return;
        }
        List<Integer> list = new ArrayList<>();
        dfs(root, list);
        TreeNode cur = root;
        for(int i = 1; i < list.size(); i ++) {
            cur.left = null;
            cur.right = new TreeNode(list.get(i));
            cur = cur.right;
        }
    }

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