199. Binary Tree Right Side View

Given A binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can SE E ordered from top to bottom.

For example:
Given The following binary tree,

   1            <---/   2     3         <---\       5     4       <---

You should return [1, 3, 4] .

The code is as follows:

1 /**2 * Definition for a binary tree node.3 * public class TreeNode {4 * int val;5 * TreeNode left;6 * TreeNode right;7 * TreeNode (int x) {val = x;}8  * }9  */Ten  Public classSolution { One      PublicList<integer>Rightsideview (TreeNode root) { A         Booleanflag=true; -List<integer> list=NewArraylist<>(); -Arraylist<treenode> res=NewArraylist<treenode>(); theMap<integer,integer> map=NewHashmap<>(); -          -         if(root==NULL) -         returnlist; +   -res=Leveltraverse (root); + List.add (root.val); AMap.put (0,0); at           -          while(flag) -         { -         while(root.right!=NULL) -        { -root=Root.right; in List.add (root.val); - Map.put (Res.indexof (Root), res.indexof (root)); to  +        } -          if(root.left!=NULL) the        { *root=Root.left; $ List.add (root.val);Panax Notoginseng Map.put (Res.indexof (Root), res.indexof (root)); -        } the        Else{ +             if(Res.indexof (Root) -1<0) Aflag=false; the             Else { +Root=res.get (Res.indexof (root)-1); -                 if(Map.containskey (Res.indexof (Root ))) $                  Break; $             } -        } -         } the         returnlist; -     }Wuyi      the      PublicArraylist<treenode> leveltraverse (TreeNode root)//horizontal traversal of the tree -     { WuArraylist<treenode> list=NewArraylist<treenode>(); -queue<treenode> queue =NewLinkedlist<treenode>(); About Queue.add (root); $          while(Queue.size () >0) -         { -TreeNode a=(TreeNode) Queue.peek (); - Queue.remove (); A List.add (a); +             if(a.left!=NULL) the Queue.add (a.left); -             if(a.right!=NULL) $ Queue.add (a.right); the         } the    the         returnlist; the     } -}

199. Binary Tree Right Side View