leetcode-226 Invert Binary Tree
- 题目描述
Invert a binary tree.
4
/ \
2 7
/ \ / \
1 3 6 9
to
4
/ \
7 2
/ \ / \
9 6 3 1
- 递归解法
用时3ms。
/**
* 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* invertTree(TreeNode* root) {
if (root == NULL)
return NULL;
TreeNode* temp = root->left;
root->left = invertTree(root->right);
root->right = invertTree(temp);
return root;
}
};
- 非递归解法
类似层次遍历，用时0ms。
/**
* 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* invertTree(TreeNode* root) {
queue<TreeNode*> q;
if (root == NULL)
return root;
q.push(root);
while (q.size() > 0){
TreeNode* temp = q.front();
q.pop();
TreeNode* left = temp->left;
temp->left = temp->right;
temp->right = left;
if (temp->left)
q.push(temp->left);
if (temp->right)
q.push(temp->right);
}
return root;
}
};