力扣二叉树简单题整理--（包含常用语法的讲解）

客卿1232026-01-26 10:47

94 二叉树的中序遍历

java 复制代码

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */


class Solution {
核心逻辑：先把所有左子节点压栈 → 弹出栈顶节点（访问值） → 处理右子节点。

public List<Integer> inorderTraversal(TreeNode root) {
        List<Integer> result=new ArrayList<>();
        inorder(root,result);
        return result;
    }
    public void inorder(TreeNode node,List<Integer> result)
    {
        if(node==null)
        {
            return;
        }
        inorder(node.left,result);
        result.add(node.val);
        inorder(node.right,result);
    }
}

104 二叉树的最大深度

java 复制代码

class Solution {
    public int maxDepth(TreeNode root) {
        if(root ==null){return 0;}
       int left= maxDepth(root.left);
       int right =maxDepth(root.right);

      return 1+ Math.max(left,right);
    }
}

3.翻转二叉树

java 复制代码

class Solution {
    public TreeNode invertTree(TreeNode root) {
        if(root == null ){return null;}

        TreeNode left=invertTree(root.left);
        TreeNode right=invertTree(root.right);

        root.left=right;
        root.right=left;
        return root;
    }
}