Invert Binary Tree, reverse Binary Tree c ++

Invert Binary Tree, reverse Binary Tree c ++

Invert a binary tree.

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

To

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

Trivia:
This problem was too red 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.

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     struct TreeNode *left; *     struct TreeNode *right; * }; */

Recursive version:

struct TreeNode* invertTree(struct TreeNode* root){    struct TreeNode *node;    if (root == NULL)        return root;    node = invertTree(root->left);    root->left = invertTree(root->right);    root->right = node;    return root;}

Non-recursive version:

struct TreeNode* invertTree(struct TreeNode *root){    struct TreeNode *node, *tmp;    Stack treeStack;    if (root == NULL)        return root;    stack_init(&treeStack, NULL);    stack_push(&treeStack, root);    while (treeStack.size > 0)    {        stack_pop(&treeStack, &node);        tmp = node->left;        node->left = node->right;        node->right = tmp;        if (node->left)            stack_push(&treeStack, node->left);        if (node->right)            stack_push(&treeStack, node->right);    }    stack_destory(&treeStack);    return root;}