Binary Tree Preorder Traversal Problem
Description
LeetCode Problem 144.
Given the root of a binary tree, return the preorder traversal of its nodes’ values.
Example 1:
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Input: root = [1,null,2,3]
Output: [1,2,3]
Example 2:
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Input: root = []
Output: []
Example 3:
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Input: root = [1]
Output: [1]
Example 4:
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Input: root = [1,2]
Output: [1,2]
Example 5:
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Input: root = [1,null,2]
Output: [1,2]
Constraints:
- The number of nodes in the tree is in the range [0, 100].
- -100 <= Node.val <= 100
Sample C++ Code
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class Solution {
public:
vector<int> preorderTraversal(TreeNode* root) {
vector<int> preorder;
if (root == NULL)
return preorder;
stack<TreeNode*> s;
s.push(root);
TreeNode* tp;
while (!s.empty()) {
tp = s.top();
s.pop();
if (tp == NULL)
continue;
s.push(tp->right);
s.push(tp->left);
preorder.push_back(tp->val);
}
return preorder;
}
};