leetcode[116]Populating Next Right Pointers in Each Node

2279 단어 LeetCode
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
    /**
    
     * 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;
    
            if(root->left)root->left->next=root->right;
    
            if(root->right&&root->next)
    
            {
    
               root->right->next=root->next->left;
    
            }
    
            connect(root->left);
    
            connect(root->right);
    
        }
    
    };

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