翻转二叉树

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翻转一棵二叉树。

样例：

1 1
/ \ / \
2 3 => 3 2
/ \
4 4

问题比较简单，这里给出递归和非递归的做法。

递归实现：

/** * Definition of TreeNode: * class TreeNode { * public: *     int val; *     TreeNode *left, *right; *     TreeNode(int val) { *         this->val = val; *         this->left = this->right = NULL; *     } * } *///递归实现void invertBinaryTree(TreeNode *root) {    if (root == NULL) return;    swap(node -> left, node -> right);    invertBinaryTree(root->left);    invertBinaryTree(root->right);}

非递归实现：

/** * Definition of TreeNode: * class TreeNode { * public: *     int val; *     TreeNode *left, *right; *     TreeNode(int val) { *         this->val = val; *         this->left = this->right = NULL; *     } * } */    //非递归实现    void invertBinaryTree(TreeNode *root) {    if (root == NULL) return;    queue<TreeNode*> level;    level.push(root);    while (!level.empty()) {         TreeNode* node = level.front();         level.pop();         swap(node->left, node->right);         if (node->left != NULL) level.push(node->left);         if (node->right != NULL) level.push(node->right);     }}

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