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.1 /** 2 * Definition for a binary tree node. 3 * struct TreeNode { 4 * int val; 5 * TreeNode *left; 6 * TreeNode *right; 7 * TreeNode(int x) : val(x), left(NULL), right(NULL) {} 8 * }; 9 */ 10 class Solution { 11 public: 12 TreeNode* invertTree(TreeNode* root) { 13 queue <TreeNode* > tree; 14 if(root==NULL) 15 return NULL; 16 tree.push(root); 17 while(!tree.empty()) 18 { 19 TreeNode* tmpnode = tree.front(); 20 tree.pop(); 21 TreeNode* left=tmpnode->left; 22 tmpnode->left=tmpnode->right; 23 tmpnode->right=left; 24 if(tmpnode->left) 25 tree.push(tmpnode->left); 26 if(tmpnode->right) 27 tree.push(tmpnode->right); 28 } 29 return root; 30 } 31 };