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06 - Morris Preorder Traversal.cpp
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06 - Morris Preorder Traversal.cpp
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/*
MORRIS PREORDER TRAVERSAL
*/
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode() : val(0), left(nullptr), right(nullptr) {}
* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
vector<int> preorderTraversal(TreeNode* root) {
vector<int> preorder;
if(root == NULL)
return preorder;
TreeNode* curr = root;
while(curr!=NULL)
{
if(curr->left == NULL)
{
preorder.push_back(curr -> val);
curr = curr -> right;
}
else
{
TreeNode* prev = curr->left;
while(prev -> right!=NULL && prev ->right!=curr)
prev = prev -> right;
if(prev -> right == NULL)
{
prev -> right = curr;
preorder.push_back(curr -> val);
curr = curr -> left;
}
else
{
prev -> right = NULL;
curr = curr -> right;
}
}
}
return preorder;
}
};