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  • 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.

    C++代码实现:

    #include<iostream>
    #include<new>
    #include<vector>
    using namespace std;
    
    //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==NULL)
                return true;
            return isSubtree(root->left,root->right);
        }
        bool isSubtree(TreeNode *root1,TreeNode *root2)
        {
            if(root1==NULL||root2==NULL)
                return (root1==NULL)&&(root2==NULL);
            return (root1->val==root2->val)&&isSubtree(root1->left,root2->right)&&isSubtree(root1->right,root2->left);
        }
        void createTree(TreeNode *&root)
        {
            int i;
            cin>>i;
            if(i!=0)
            {
                root=new TreeNode(i);
                if(root==NULL)
                    return;
                createTree(root->left);
                createTree(root->right);
            }
        }
    };
    
    int main()
    {
        Solution s;
        TreeNode *root;
        s.createTree(root);
        cout<<s.isSymmetric(root)<<endl;
    }

    总结:二叉树的相似、同构、镜像,3种类型。。

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  • 原文地址:https://www.cnblogs.com/wuchanming/p/4102987.html
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