#Leetcode# 144. Binary Tree Preorder Traversal
发布时间：2020-12-14 04:27:35 所属栏目：大数据 来源：网络整理
导读：https://leetcode.com/problems/binary-tree-preorder-traversal/ ? Given a binary tree,return the? preorder ?traversal of its nodes‘ values. Example: Input:? 1 2 / 3Output:?[1,null,2,3][1,3] Follow up:?Recursive solution is trivial,could you
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https://leetcode.com/problems/binary-tree-preorder-traversal/ ? Given a binary tree,return the?preorder?traversal of its nodes‘ values. Example: Input:?
1
2
/
3
Output:?
[1,null,2,3][1,3]
Follow up:?Recursive solution is trivial,could you do it iteratively? 代码： /**
* Definition for a binary tree node.
* 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) {
vector<int> ans;
if(!root) return ans;
pre(ans,root);
return ans;
}
void pre(vector<int>& ans,TreeNode* root) {
ans.push_back(root -> val);
if(root -> left)
pre(ans,root -> left);
if(root -> right)
pre(ans,root -> right);
}
};
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