# Leetcode #145 Binary Tree postorder Traversal

Source: Internet
Author: User

(Non-recursive implementation) the sequential traversal of a binary tree.

`1 classSolution2 {3  Public:4vector<int> Postordertraversal (TreeNode *root)5     {6vector<int>output;7         if(Root = =NULL)8         {9             returnoutput;Ten         } One  AStack<treenode*>Nodestack; -TreeNode *recentlyvisited =NULL; -  the          while(Root! = NULL | |!nodestack.empty ()) -         { -             if(Root! =NULL) -             { + Nodestack.push (root); -root = root->left;//find the left-most leaf node.  +             } A             Else //The left dial hand tree is empty.  at             { -root = Nodestack.top ();//rolls back a node.  -                 if(Root->right! = NULL && root->right! = recentlyvisited)//the right subtree is not empty and has not been accessed.  -                 { -root = root->Right ; - Nodestack.push (root); inroot = root->Left ; -                 } to                 Else //the right subtree is empty or has been visited.  +                 { -root = Nodestack.top ();//rolls back a node.  theNodestack.pop ();//Remove the node from the stack (just back off, not deleted).  *Output.push_back (Root->val);//outputs the node.  \$recentlyvisited = root;//record the access to the right subtree (the recording process is bottom-up). Panax Notoginsengroot = NULL;//The left and right subtree output is complete, resetting the node and assigning it to the node at the top of the stack the next time it enters the loop.  -                 } the             } +         } A  the         returnoutput; +     } -};`

Leetcode #145 Binary Tree postorder Traversal

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