46 lines
1.1 KiB
C++
46 lines
1.1 KiB
C++
#include <iostream>
|
|
#include <stack>
|
|
|
|
class TreeNode {
|
|
public:
|
|
int val;
|
|
TreeNode* left;
|
|
TreeNode* right;
|
|
TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
|
|
};
|
|
|
|
// pre order traverse a binary tree, iteratively.
|
|
void preorderTraversal(TreeNode* root) {
|
|
if (root == nullptr) return;
|
|
|
|
std::stack<TreeNode*> st;
|
|
st.push(root);
|
|
|
|
while (!st.empty()) {
|
|
TreeNode* current = st.top();
|
|
st.pop();
|
|
std::cout << current->val << " ";
|
|
|
|
if (current->right) st.push(current->right); // push right first
|
|
if (current->left) st.push(current->left); // then push left
|
|
}
|
|
}
|
|
|
|
int main() {
|
|
TreeNode* root = new TreeNode(1);
|
|
root->left = new TreeNode(2);
|
|
root->right = new TreeNode(3);
|
|
root->left->left = new TreeNode(4);
|
|
root->left->right = new TreeNode(5);
|
|
root->left->right->left = new TreeNode(6);
|
|
root->left->right->right = new TreeNode(7);
|
|
root->right->right = new TreeNode(8);
|
|
root->right->right->left = new TreeNode(9);
|
|
|
|
std::cout << "Inorder Traversal: ";
|
|
preorderTraversal(root);
|
|
std::cout << std::endl;
|
|
|
|
return 0;
|
|
}
|