标签：des style blog io ar color sp for on
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?
分析：迭代版先序遍历。用一个栈保存结点，压栈顺序为先右子树后左子树。时间复杂度为O(n)，空间复杂度为O(h)。代码如下：
class Solution { public: vector<int> preorderTraversal(TreeNode *root) { vector<int> result; if(!root) return result; stack<TreeNode *> S; S.push(root); while(!S.empty()){ TreeNode *tmp = S.top(); result.push_back(tmp->val); S.pop(); if(tmp->right) S.push(tmp->right); if(tmp->left) S.push(tmp->left); } return result; } };
Leetcode: Binary Tree Preorder Traversal
标签：des style blog io ar color sp for on
原文地址：http://www.cnblogs.com/Kai-Xing/p/4143783.html
