给定一棵二叉树的根节点 root
,请左右翻转这棵二叉树,并返回其根节点。
示例 1:
输入:root = [5,7,9,8,3,2,4] 输出:[5,9,7,4,2,3,8]
提示:
- 树中节点数目范围在
[0, 100]
内 -100 <= Node.val <= 100
题解
前序遍历图解
代码
递归算法
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
TreeNode* mirrorTree(TreeNode* root) {
if(!root) return nullptr;
swap(root->left,root->right);
mirrorTree(root->left);
mirrorTree(root->right);
return root;
}
};
非递归算法
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
TreeNode* mirrorTree(TreeNode* root) {
if(!root) return nullptr;
stack<TreeNode*> s;
s.push(root);
while(!s.empty())
{
TreeNode* node=s.top();
s.pop();
swap(node->left,node->right);
if(node->left) s.push(node->left);
if(node->right) s.push(node->right);
}
return root;
}
};