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  • [leetcode]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
    

     

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

     

    /**
     * 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 sym(TreeNode *root1, TreeNode *root2){
            if(!root1 && !root2) return true;
            if(!root1 || !root2) return false;
            
            if(root1->val != root2->val) return false;
            
            if(!sym(root1->left,root2->right)) return false;
            if(!sym(root1->right,root2->left)) return false;
    
            return true;
            
        }
    
        bool isSymmetric(TreeNode *root) {
            // Start typing your C/C++ solution below
            // DO NOT write int main() function
            if(!root) return true;
            return sym(root->left, root->right);
        }
    };


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  • 原文地址:https://www.cnblogs.com/snake-hand/p/3172450.html
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