［LeetCode］Populating Next Right Pointers in Each Node

解题思路：

宽度搜索。

1，增加一个queue记录height；

2，从queue出来的node，如果与前一个node的height一样，则让前一个node->next = curnode；

3，每次循环，都更新preNode 和preHeight;

/**
 * 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) {
        queue<TreeLinkNode* > qNodes;
        queue<int>            qHeight;

        qNodes.push(root);
        qHeight.push(0);
        TreeLinkNode* preNode = NULL;
        int preHeight = -1;
        while(!qNodes.empty()){
            TreeLinkNode* curNode = qNodes.front(); qNodes.pop();
            int curHeight = qHeight.front(); qHeight.pop();
            if (curNode != NULL){
                if (curHeight == preHeight){
                    preNode->next = curNode;
                }
                preNode = curNode;
                preHeight = curHeight;

                qNodes.push(curNode->left);
                qHeight.push(curHeight + 1);

                qNodes.push(curNode->right);
                qHeight.push(curHeight + 1);
            }
        }
    }
};