题目描述 牛客网

• 从上到下按层打印二叉树，同一层的节点按从左到右的顺序打印，每一层打印到一行

• 如下图打印结果为

8 
6    10
5    7     9    11

题目解读

• 剑指Offer 174

代码

• 第一轮代码

void PrintFromTopToBottom(TreeNode* root){
    if(root == NULL){
            // 二叉树为空，什么也不用做...
    }
    else{
        queue<TreeNode *> que;
        que.push(root);
        int toBePrint = 1;
        int nextLevel = 0;
        while(que.size()){
            TreeNode *temp = que.front();
            cout<<temp -> val<<" ";
            toBePrint --;
            que.pop();

            if(temp -> left){
                que.push(temp -> left);
                nextLevel ++;
            }

            if(temp -> right){
                que.push(temp -> right);
                nextLevel ++;
            }

            if(toBePrint == 0){
                cout<<endl;
                toBePrint = nextLevel;
                nextLevel = 0;
            }
        }

    }
}

• 第二轮代码

class Solution {
public:
        vector<vector<int> > Print(TreeNode* pRoot) {
            vector<vector<int> > result;
            vector<int> temp;
            deque<TreeNode* > que;
            int tobePrint = 1;
            int nextLevel = 0;
            
            if(pRoot == NULL){
                return result;
            }
            que.push_back(pRoot);
            while(!que.empty()){
                TreeNode* tt = que.front();
                que.pop_front();
                temp.push_back(tt->val);
                tobePrint--;
                
                if(tt->left != NULL){
                    que.push_back(tt->left);
                    nextLevel++;
                }
                
                if(tt->right != NULL){
                    que.push_back(tt->right);
                    nextLevel++;
                }
                
                if(tobePrint == 0){
                    tobePrint = nextLevel;
                    nextLevel = 0;
                    result.push_back(temp);
                    temp.clear();
                }
            }
            return result;
        }
};

总结展望

• 思路很好，以前感觉自己编程能力很好，现在感觉也就一般般，唉，努力努力再努力