[Tree] Binary Tree Preorder Traversal

Total accepted:97599 Total submissions:257736 difficulty:medium

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 do it iteratively?

(m) binary Tree inorder traversal (m) Verify preorder Sequence in Binary Search Tree

/** Definition for a binary tree node. * struct TreeNode {* int val; * TreeNode *left; * TreeNode *right; * TreeNode (int x): Val (x), left (null), right (NULL) {} *}; */classSolution { Public: Vector<int> Preordertraversal (treenode*root) {Vector<int>Res; TreeNode* p =Root; if(p==NULL) {            returnRes; } Stack<TreeNode*>Stk;  while(P | |!Stk.empty ()) {             while(P) {Res.push_back (P-val);                Stk.push (P); P=p->Left ; }            if(!Stk.empty ()) {P= Stk.top ()Right ;            Stk.pop (); }        }        returnRes; }};

Next challenges: (m) Binary Tree inorder Traversal (m) Verify preorder Sequence in Binary Search Tree

[Tree] Binary Tree Preorder Traversal