* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector preorderTraversal(TreeNode *root) {
// IMPORTANT: Please reset any member data you declared, as
// the same Solution instance will be reused for each test case.
vector result;
stack nodeStack;
TreeNode* curNode = root;
while(curNode || !nodeStack.empty())
{
if(curNode) result.push_back(curNode->
val);
//...process left recursive call
while(curNode)
{
nodeStack.push(curNode);
curNode = curNode->left;
if(curNode) result.push_back(curNode->val);
}
//..process the rest after left recursive call
if(!nodeStack.empty())
{
curNode = nodeStack.top();
nodeStack.pop();
curNode = curNode->right;
}
}
return result;
}
};