59把二叉树打印成多行

题目描述

从上到下按层打印二叉树，同一层结点从左至右输出。每一层输出一行。

 

思路：二叉树的层次遍历。

/*
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 == nullptr){
                return res;
            }
            queue<TreeNode*> q;
            q.push(pRoot);
            while(!q.empty()){
                int sz = q.size();
                vector<int> tmp;
                for(int i = 0;i < sz;++i){
                    TreeNode* tmpNode = q.front();
                    q.pop();
                    tmp.push_back(tmpNode->val);
                    if(tmpNode->left){
                        q.push(tmpNode->left);
                    }
                    if(tmpNode->right){
                        q.push(tmpNode->right);
                    }
                }
                res.push_back(tmp);
            }
            return res;
        }
    
};