Leetcode-binary Tree Vertical Order traversal

Given a binary tree, return the vertical order Traversal of its nodes ' values. (ie, from top to bottom, and column by column).

If the nodes is in the same row and column, the order should is from left to right.

Examples:

1. Given binary Tree [3,9,20,null,null,15,7] ,
   

      3  //   9    /   /   7

   Return its vertical order traversal as:
   

   [  9],  [3,15],  [+],  [7]]

2. Given binary Tree [3,9,8,4,0,1,7] ,
   

        3    /   /     9   8  /\  //  /   4   7

   Return its vertical order traversal as:
   

   [  4],  [9],  [3,0,1],  [8],  [7]]

3. Given binary Tree [3,9,8,4,0,1,7,null,null,null,2,5] (0 ' s right child was 2 and 1 ' s left child is 5),
   

        3    /   /     9   8  /\  //  /   4  7    /   /     5   2

   Return its vertical order traversal as:
   

   [  4],  [9,5],  [3,0,1],  [8,2],  [7]]

Analysis:note in the second example, 2 was in the left subtree of root, but would after 8 in the results. So simple traverse. We can use the BFS with index recording. Solution:

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<list<integer>>Verticalorder (TreeNode root) { AList<list<integer>> reslist =NewArraylist<list<integer>>(); -         if(root==NULL)returnreslist; -  theList<treenode> nodeList =NewArraylist<treenode>(); -List<integer> indexlist =NewArraylist<integer>(); -         intCur = 0, min = 0, max=0; - Nodelist.add (root); +Indexlist.add (0); -      +          while(cur<nodelist.size ()) { ATreeNode Curnode =nodelist.get (cur); at             intCurindex =indexlist.get (cur); -             if(Curindex < min) min =Curindex; -             if(Curindex > Max) max =Curindex; -  -             if(curnode.left!=NULL){ - Nodelist.add (curnode.left); inIndexlist.add (curIndex-1); -             } to             if(curnode.right!=NULL){ + Nodelist.add (curnode.right); -Indexlist.add (curindex+1); the             } *cur++; $         }Panax Notoginseng          -          for(inti=min;i<=max;i++) Reslist.add (NewLinkedlist<integer>()); the          +          for(intI=0;i<nodelist.size (); i++){ AReslist.get (Indexlist.get (i)-min). Add (Nodelist.get (i). val); the         } +  -          $         returnreslist; $     } -          -}

Leetcode-binary Tree Vertical Order traversal