Leetcode:Populating Next Right Pointers in Each Node

标签：populating next righ

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 to NULL.

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

基本思路：从每层的最左边开始遍历该层的每一个结点，指定该结点的next。

实现代码：

/**
 * Definition for binary tree with next pointer.
 * struct TreeLinkNode {
 *  int val;
 *  TreeLinkNode *left, *right, *next;
 *  TreeLinkNode(int x) : val(x), left(NULL), right(NULL), next(NULL) {}
 * };
 */
class Solution {
public:
    void connect(TreeLinkNode *root) {
        if(root==NULL)  return;
        TreeLinkNode *leftBegin=root;
        while(leftBegin!=NULL)
        {
            TreeLinkNode *across=leftBegin;
            while(across!=NULL)
            {
                if(across->left!=NULL)
                    across->left->next=across->right;
                if(across->right!=NULL&&across->next!=NULL)
                    across->right->next=across->next->left;
                    
                across=across->next;
            }
            leftBegin=leftBegin->left;
        }
    }
};

Leetcode:Populating Next Right Pointers in Each Node

标签：populating next righ

原文地址：http://blog.csdn.net/wolongdede/article/details/44728833