[LeetCode-116] Populating Next Right Pointers in Each Node
Populating Next Right Pointers in Each Node
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
.
Note:
- You may only use constant extra space.
- You may assume that it is a perfect binary tree (ie, all leaves are at the same level, and every parent has two children).
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
嗯。。。看代码吧。。。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
1 /** 2 * Definition for binary tree with next pointer. 3 * struct TreeLinkNode { 4 * int val; 5 * TreeLinkNode *left, *right, *next; 6 * TreeLinkNode(int x) : val(x), left(NULL), right(NULL), next(NULL) {} 7 * }; 8 */ 9 class Solution { 10 public: 11 void connect(TreeLinkNode *root) { 12 // Start typing your C/C++ solution below 13 // DO NOT write int main() function 14 if (NULL == root) { 15 return; 16 } 17 vector<TreeLinkNode*> node_vec_a(1, root); 18 vector<TreeLinkNode*> node_vec_b; 19 bool flag = true; 20 vector<TreeLinkNode*> *pvec_last = NULL, *pvec_cur = NULL; 21 for (;;) { 22 if (flag) { 23 pvec_last = &node_vec_a; 24 pvec_cur = &node_vec_b; 25 } else { 26 pvec_last = &node_vec_b; 27 pvec_cur = &node_vec_a; 28 } 29 flag = !flag; 30 pvec_cur->clear(); 31 if (0 == pvec_last->size()) { 32 break; 33 } 34 for (vector<TreeLinkNode*>::iterator iter = pvec_last->begin(); 35 iter != pvec_last->end(); ++iter) { 36 if (NULL != (*iter)->left) { 37 pvec_cur->push_back((*iter)->left); 38 } 39 if (NULL != (*iter)->right) { 40 pvec_cur->push_back((*iter)->right); 41 } 42 } 43 for (vector<TreeLinkNode*>::iterator iter = pvec_cur->begin(); 44 iter != pvec_cur->end(); ++iter) { 45 (*iter)->next = ((pvec_cur->end() == (iter + 1)) ? NULL : *(iter + 1)); 46 } 47 } 48 } 49 };