Invert Binary Tree Solutions in C++

// Source : https://leetcode.com/problems/invert-binary-tree/
// Author : Hao Chen
// Date   : 2015-06-12



/**
 * 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);    
    }
};

/// Source : https://leetcode.com/problems/invert-binary-tree/description/
/// Author : liuyubobobo
/// Time   : 2017-11-17

#include <iostream>

using namespace std;


/// Definition for a binary tree node.
struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

/// Recursive
/// Time Complexity: O(n), where n is the node's number of the tree
/// Space Complexity: O(h), where h is the height of the tree
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {

        if(root == NULL)
            return NULL;

        invertTree(root->left);
        invertTree(root->right);
        swap(root->left, root->right);

        return root;
    }
};

int main() {

    return 0;
}

/// Source : https://leetcode.com/problems/invert-binary-tree/description/
/// Author : liuyubobobo
/// Time   : 2017-11-17

#include <iostream>
#include <queue>

using namespace std;


/// Definition for a binary tree node.
struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

/// Non-Recursive
/// Time Complexity: O(n), where n is the node's number of the tree
/// Space Complexity: O(n)
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {

        if(root == NULL)
            return NULL;

        queue<TreeNode*> q;
        q.push(root);
        while(!q.empty()){
            TreeNode* curNode = q.front();
            q.pop();
            swap(curNode->left, curNode->right);

            if(curNode->left)
                q.push(curNode->left);
            if(curNode->right)
                q.push(curNode->right);
        }

        return root;
    }
};

int main() {

    return 0;
}