Eric 的小站

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输入：root = [4,2,7,1,3,6,9]
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输出：[4,7,2,9,6,3,1]

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输入：root = [2,1,3]
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输出：[2,3,1]

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/**
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 * Definition for a binary tree node.
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 * struct TreeNode {
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 *     int val;
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 *     TreeNode *left;
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 *     TreeNode *right;
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 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
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 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
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 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
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 * };
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 */
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class Solution {
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public:
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    TreeNode* invertTree(TreeNode* root) {
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        if(root == nullptr) return root;
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        TreeNode* Tmp = root->left;
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        root->left = invertTree(root->right);
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        root->right = invertTree(Tmp);
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        return root;
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    }
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};