226. Invert Binary Tree
Easy
Invert a binary tree.
Example:
Input:
4 / \ 2 7 / \ / \ 1 3 6 9
Output:
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 f*** off.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | //C++: 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) { if(!root) return NULL; TreeNode *tmp = root->left; root->left = invertTree(root->right); root->right = invertTree(tmp); return root; } }; |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode() {} * TreeNode(int val) { this.val = val; } * TreeNode(int val, TreeNode left, TreeNode right) { * this.val = val; * this.left = left; * this.right = right; * } * } */ class Solution { public TreeNode invertTree(TreeNode root) { if(root==null) return null; TreeNode left = invertTree(root.left); TreeNode right = invertTree(root.right); root.left = right; root.right = left; return root; } } |
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