首页 > 代码库 > LeetCode Symmetric Tree

LeetCode Symmetric Tree

2024-07-25 08:25:30   219人阅读

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

For example, this binary tree is symmetric:

    1   /   2   2 / \ / 3  4 4  3

 

But the following is not:

    1   /   2   2   \      3    3

 

Note:
Bonus points if you could solve it both recursively and iteratively.

 

 

题意为判断一颗二叉树是不是对称的。

解法是递归，一颗二叉树对称，必须是其左右孩子互相对称，左孩子的左子树对称于右孩子的右子树，左孩子的右子树对称于右孩子的左子树。

 

 1 /** 2  * Definition for binary tree 3  * public class TreeNode { 4  *     int val; 5  *     TreeNode left; 6  *     TreeNode right; 7 *     TreeNode(int x) { val = x; }      8  * } 9  */10 public class Solution {11     12     private boolean isChildSymmetric(TreeNode root1,TreeNode root2) {13         if (root1==null && root2==null) {14             return true;15         }16         if (root1==null || root2==null) {17             return false;18         }19         if (root1.val==root2.val) {20             if (isChildSymmetric(root1.left, root2.right) && isChildSymmetric(root1.right, root2.left)) {21                 return true;22             } else {23                 return false;24             }25         } else {26             return false;27         }28     }29     30     31     public boolean isSymmetric(TreeNode root) {32         if (root == null) {33             return true;34         }35         return isChildSymmetric(root.left, root.right);36     }37 }

 

LeetCode Symmetric Tree


联系
我们