leetcode_question_116 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 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

BFS:
/**
 * 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) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if(root==NULL)return;
    	vector<TreeLinkNode*> vec;
		vec.push_back(root);
		int count = 1;
		while(!vec.empty())
		{
			if(count > 1) vec[0]->next = vec[1];
			else vec[0]->next = NULL;
			if(vec[0]->left) vec.push_back(vec[0]->left);
			if(vec[0]->right) vec.push_back(vec[0]->right);
			vec.erase(vec.begin());
			count--;

			if(count == 0)
				count = vec.size();
		}
    }
};

좋은 웹페이지 즐겨찾기