【剑指Offer】（树）按之字形顺序打印二叉树

我会带着你远行 2022-03-16 01:00 182阅读 0赞

**题目链接**：[https://www.nowcoder.com/practice/91b69814117f4e8097390d107d2efbe0?tpId=13&tqId=11212&tPage=3&rp=3&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking][https_www.nowcoder.com_practice_91b69814117f4e8097390d107d2efbe0_tpId_13_tqId_11212_tPage_3_rp_3_ru_ta_coding-interviews_qru_ta_coding-interviews_question-ranking]

#### 题目描述 ####

请实现一个函数按照之字形打印二叉树，即第一行按照从左到右的顺序打印，第二层按照从右至左的顺序打印，第三行按照从左到右的顺序打印，其他行以此类推。

#### 解决方法 ####

/* 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) { 
            vector<vector<int>> res;
            if(!pRoot) return res;
            queue<TreeNode*> q;
            q.push(pRoot);
            bool flag=false;
            while(!q.empty()){ 
                vector<int> resL;
                int len=q.size();
                while(len--){ 
                    TreeNode *temp=q.front(); q.pop();                
                    resL.push_back(temp->val);
                    if(temp->left) q.push(temp->left);
                    if(temp->right) q.push(temp->right);
                }
                if(flag) reverse(resL.begin(),resL.end());//数组反向
                flag=!flag;
                res.push_back(resL);
            }
            return res;
        }
        
    };

[https_www.nowcoder.com_practice_91b69814117f4e8097390d107d2efbe0_tpId_13_tqId_11212_tPage_3_rp_3_ru_ta_coding-interviews_qru_ta_coding-interviews_question-ranking]: https://www.nowcoder.com/practice/91b69814117f4e8097390d107d2efbe0?tpId=13&tqId=11212&tPage=3&rp=3&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking