binary-tree-preorder-traversal，前序输出

给定一个二叉树，前序输出 /** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ #include<stack> class Solution { public: vector<int> preorderTraversal(TreeNode *root) { vector<int> temp_v; if(root==NULL) return temp_v; stack<TreeNode*> temp_stack; temp_stack.push(root); while(!temp_stack.empty()) { TreeNode* temp_p=temp_stack.top(); temp_stack.pop(); temp_v.push_back(temp_p->val); if(temp_p->right!=NULL) temp_stack.push(temp_p->right); if(temp_p->left!=NULL) temp_stack.push(temp_p->left); } return temp_v; } };