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Copy pathInvertBinaryTree.cpp
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71 lines (65 loc) · 1.84 KB
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// Source : https://leetcode.com/problems/invert-binary-tree/
// Author : Hao Chen
// Date : 2015-06-12
/**********************************************************************************
*
* 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:
* (https://twitter.com/mxcl/status/608682016205344768)
*
* | 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.
*
**********************************************************************************/
/**
* 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_recursive(TreeNode* root) {
if (root==NULL) return root;
TreeNode* node = invertTree_recursive(root->left);
root->left = invertTree_recursive(root->right);
root->right = node;
return root;
}
TreeNode* invertTree_non_recursive(TreeNode* root) {
if (root==NULL) return root;
vector<TreeNode*> stack;
stack.push_back(root);
while (!stack.empty()) {
TreeNode* node = stack.back();
stack.pop_back();
swap(node->left, node->right);
if (node->left) stack.push_back(node->left);
if (node->right) stack.push_back(node->right);
}
return root;
}
TreeNode* invertTree(TreeNode* root) {
if (rand()%2){
return invertTree_non_recursive(root);
}
return invertTree_recursive(root);
}
};