# 226. Invert Binary Tree

Invert a binary tree.

``````     4
/   \
2     7
/ \   / \
1   3 6   9
``````

to

``````     4
/   \
7     2
/ \   / \
9   6 3   1
``````

Trivia:
This problem was inspired by this original tweet by Max Howell:

Google: 90% of our engineers use the software you wrote (Homebrew), but you can’t invert a binary tree on a whiteboard so fuck off.

``````// Recursion
class Solution {
public:
TreeNode* invertTree(TreeNode* root) {
if (!root) return NULL;
TreeNode *tmp = root->left;
root->left = invertTree(root->right);
root->right = invertTree(tmp);
return root;
}
};
``````

``````// Non-Recursion
class Solution {
public:
TreeNode* invertTree(TreeNode* root) {
if (!root) return NULL;
queue<TreeNode*> q;
q.push(root);
while (!q.empty()) {
TreeNode *node = q.front(); q.pop();
TreeNode *tmp = node->left;
node->left = node->right;
node->right = tmp;
if (node->left) q.push(node->left);
if (node->right) q.push(node->right);
}
return root;
}
};
``````

LeetCode All in One 题目讲解汇总(持续更新中…)

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