connect2.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) {
        TreeLinkNode *now, *tail, *head;

        now = root;
        head = tail = NULL;
        while(now)
        {
            if (now->left)
                if (tail) tail = tail->next =now->left;
                else head = tail = now->left;
            if (now->right)
                if (tail) tail = tail->next =now->right;
                else head = tail = now->right;
            if(!(now = now->next))
            {
                now = head;
                head = tail=NULL;
            }
        }
    }
};