剑指offer——34之字打印二叉树

 1 class Solution {
 2 public:
 3     vector<vector<int> > Print(TreeNode* pRoot) {
 4         vector<vector<int>>res;
 5         BFS(pRoot, res);
 6         return res;
 7     }
 8     void BFS(TreeNode *root, vector<vector<int>>&res)
 9     {
10         if (root == nullptr)return;
11         queue<TreeNode*>q;
12         q.push(root);
13         bool fromLeft = true;
14         while (!q.empty())
15         {
16             queue<TreeNode*>temp;
17             vector<int>v;
18             while (!q.empty())
19             {
20                 TreeNode* p = q.front();
21                 q.pop();
22                 v.push_back(p->val);
23                 if (p->left != nullptr)temp.push(p->left);
24                 if (p->right != nullptr)temp.push(p->right);
25             }
26             if(fromLeft)
27                 res.push_back(v);
28             else
29             {
30                 reverse(v.begin(), v.end());
31                 res.push_back(v);
32             }
33             fromLeft = !fromLeft;
34             q = temp;
35         }
36     }
37 };
38