leetcode@ [116/117] Populating Next Right Pointers in Each Node I & II (Tree, 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 node {
    public:
        TreeLinkNode* nd; 
        int lv;
        node(TreeLinkNode* rhs, int l): nd(rhs), lv(l) {}
};

class Solution {
public:
    void connect(TreeLinkNode *root) {
        if(!root)  return;
        
        queue<node> q;
        q.push(node(root, 0));
        vector<node> vec;
        
        while(!q.empty()) {
            node top = q.front();
            vec.push_back(top);
            q.pop();
            
            int cur_lv = top.lv;
            TreeLinkNode* cur_nd = top.nd;
            
            if(cur_nd->left)  q.push(node(cur_nd->left, cur_lv+1));
            if(cur_nd->right)  q.push(node(cur_nd->right, cur_lv+1));
        }
        
        int l = 0, r = 1;
        while(r < vec.size()) {
            vec[l].nd->next = NULL;
            while(r < vec.size() && vec[r].lv == vec[l].lv) {
                vec[l].nd->next = vec[r].nd;
                ++l;
                ++r;
            }
            
            l = r;
            r = l+1;
        }
        vec[vec.size()-1].nd->next = NULL;
    }
};