劍指offer_編程題_把二叉樹打印成多行

• 題目

  從上到下按層打印二叉樹，同一層結點從左至右輸出。
  每一層輸出一行。
  

1. 按層序遍歷

   /*
   struct TreeNode {
       int val;
       struct TreeNode *left;
       struct TreeNode *right;
       TreeNode(int x) :
               val(x), left(NULL), right(NULL) {
       }
   };
   */
   class Solution {
   public:
           vector<vector<int> > Print(TreeNode* pRoot) {
               std::vector<std::vector<int>> res;
        	   if (pRoot==NULL)
        		   return res;
        	   std::queue<TreeNode*> q;
        	   q.push(pRoot);
        	   while(!q.empty())
        	   {
        		   int length = q.size();
        		   std::vector<int> temp;
        		   for (int i = 0; i < length; ++i)
        		   {
        			   TreeNode* now = q.front();
        			   temp.push_back(now->val);
        			   q.pop();
        			   if (now->left!=NULL)
        				   q.push(now->left);
        			   if (now->right!=NULL)
        				   q.push(now->right);
        		   }
        		   res.push_back(temp);
        	   }
        	   return res;
           }
   };