Leetcode:Symmetric Tree 判断对称树

Symmetric Tree

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
 
/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool isSymmetric(TreeNode *root) {
        if (root == nullptr) return true;
        return SymmeFunc(root->left, root->right);
    }
    bool SymmeFunc(TreeNode* left, TreeNode* right) {
        if (left == nullptr && right == nullptr) {
            return true;
        } else if (left != nullptr && right != nullptr) {
            return ((left->val == right->val) && SymmeFunc(left->left, right->right) && SymmeFunc(left->right, right->left));
        } else {
            return false;
        }
    }
};

解题分析:递归判断二叉树A的左子树和二叉树B的右子树

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