感想

一轮AC

• 代码虽小 五脏俱全
• bfs最小模板的认识
• queue的掌握认识
• 各种层次遍历的基础

code

/*
struct TreeNode {
	int val;
	struct TreeNode *left;
	struct TreeNode *right;
	TreeNode(int x) :
			val(x), left(NULL), right(NULL) {
	}
};*/
class Solution {
public:
    vector<int> PrintFromTopToBottom(TreeNode* root) {
    
        vector<int> vec;
        //bfs mode
        if(!root){
            return vec;
        }
        
        queue<TreeNode*> q;
        q.push(root);
        
        while(!q.empty()){
            TreeNode* top = q.front();
            vec.push_back(top->val);
            q.pop();
            
            //no level control ,while(sz)
            if(top->left){
                q.push(top->left);
            }
            if(top->right){
                q.push(top->right);
            }
            
        }
        
        return vec;
    }
};