94 Binary Tree Inorder Traversal

LeetCode

Given the root of a binary tree, return the inorder traversal of its nodes' values.

Example 1:

Input: root = [1,null,2,3] Output: [1,3,2]

Example 2:

Input: root = [] Output: []

Example 3:

Input: root = [1] Output: [1]

Example 4:

Input: root = [1,2] Output: [2,1]

Example 5:

Input: root = [1,null,2] Output: [1,2]

Constraints:

The number of nodes in the tree is in the range [0, 100]. -100 <= Node.val <= 100

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很简单，建一个 List ，中序遍历时加入 List 即可

import java.util.LinkedList;
class Solution {
    List<Integer> list;
    public List<Integer> inorderTraversal(TreeNode root) {
        
        list=new LinkedList<>();
        if(root==null) return list;
        inOrder(root);
        return list;
    }
    public void inOrder(TreeNode t){
        if(t.left!=null) inOrder(t.left);
        list.add(t.val);
        if(t.right!=null) inOrder(t.right);
    }
}