Binary Tree Preorder Traversal
Given a binary tree, return the preorder traversal of its nodes' values.
For example:
Given binary tree {1,#,2,3}
,
1 \ 2 / 3
return [1,2,3]
.
Note: Recursive solution is trivial, could you do it iteratively?
思路:
深度优先搜索用栈进行。
题解:
/**
* 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<int> preorderTraversal(TreeNode *root) {
if (root == nullptr)
return vector<int>();
vector<int> values;
stack<TreeNode*> visits;
visits.push(root);
while(!visits.empty())
{
auto node = visits.top();
visits.pop();
values.push_back(node->val);
if (node->right) visits.push(node->right);
if (node->left) visits.push(node->left);
}
return values;
}
};