day44（12.25）——leetcode面试经典150

努力学算法的蒟蒻2025-12-26 17:09

100. 相同的树

这几题都比较好写，心情愉悦

题目：

题解：

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 {
    public boolean flag = true;
    public void simple(TreeNode p, TreeNode q) {
        if(flag == false) {
            return;
        }
        if((p == null && q != null) || (p != null && q == null)) {
            flag = false;
            return;
        }
        else if(p == null && q == null) {
            return;
        }
        else if(p.val != q.val) {
            flag = false;
            return;
        }
        simple(p.left,q.left);
        simple(p.right,q.right);

    }

    public boolean isSameTree(TreeNode p, TreeNode q) {
        simple(p,q);
        return flag;
    }
}

226. 翻转二叉树

题目：

题解：

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 {
    public void dfs(TreeNode root) {
        if(root == null) {
            return ;
        }
        TreeNode t = root.left;
        root.left = root.right;
        root.right = t;
        dfs(root.left);
        dfs(root.right); 
    } 

    public TreeNode invertTree(TreeNode root) {
        dfs(root);
        return root;
    }
}