[Tree] Binary Tree Preorder Traversal

Source: Internet
Author: User

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

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