LeetCode Populating Next Right Pointers in Each Node

Description

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.

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

The original problem is here.

The original code is here.

My Solution

I solve this problem in C++, as below:

/*
*Populating Next Right Pointers in Each Node 
*Author: shuaijiang
*Email: zhaoshuaijiang8@gmail.com
*/
#include<iostream>
#include<vector>
#include<stdlib.h>
using namespace std;

/**
 * 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;
        vector<TreeLinkNode*> currLevel;
        vector<TreeLinkNode*> nextLevel;
        currLevel.push_back(root);
        while(currLevel.size()>0){
            for(int i=0;i<currLevel.size();i++){
                TreeLinkNode * node = currLevel[i];
                if(i+1<currLevel.size())
                    node->next = currLevel[i+1];
                if(node->left != NULL)
                    nextLevel.push_back(node->left);
                if(node->right != NULL)
                    nextLevel.push_back(node->right);
            }
            currLevel = nextLevel;
            nextLevel.clear();
        }
    }
};

Note

To solve the problem, I use a vector to save the nodes of each level, and Populat next pointer of each node to point to its next right node.