116 Populating Next Right Pointers in Each.cpp

/**
 * 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 *pre = root;
        TreeLinkNode *cur = NULL;
        while(pre->left)
        {
            cur = pre;
            while(cur)
            {
                cur->left->next = cur->right;
                if(cur->next) cur->right->next = cur->next->left;
                cur = cur->next;
            }
            pre = pre->left;
        }
    }
};