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Tuesday, December 11, 2012

LeetCode:Populating Next Right Pointers in Each Node

Populating Next Right Pointers in Each Node
Given a binary tree
    struct TreeLinkNode {
      TreeLinkNode *left;
      TreeLinkNode *right;
      TreeLinkNode *next;
    }
Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set toNULL.
Initially, all next pointers are set to NULL.
Note:
  • You may only use constant extra space.
  • You may assume that it is a perfect binary tree (ie, all leaves are at the same level, and every parent has two children).
For example,
Given the following perfect binary tree,
         1
       /  \
      2    3
     / \  / \
    4  5  6  7
After calling your function, the tree should look like:
         1 -> NULL
       /  \
      2 -> 3 -> NULL
     / \  / \
    4->5->6->7 -> NULL

public class Solution {
    public void connect(TreeLinkNode root) {
        // Start typing your Java solution below
        // DO NOT write main() function
        if(root==null) return;
        TreeLinkNode cur=root, 
                     top=root, 
                     first=root.left;
        cur.next = null;
        
        while(top!=null && top.left!=null){
            while(top!=null){
                cur=top.left;
                cur.next=top.right;
                cur=cur.next;
                top=top.next;
                cur.next=(top==null)?null:top.left;
            }
            top=first;
            first=(top==null)?null:top.left;
        }
        
    }
}

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