题解 | #求二叉树的层序遍历#

//c++递归的方法
/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 * };
 */

#include <cstddef>
#include <vector>
class Solution {
public:
    /**
     * 
     * @param root TreeNode类 
     * @return int整型vector<vector<>>
     */
    void recursionOrder(vector<vector<int>> &res,TreeNode* root,int depth){
        if (root) {
            if(res.size()<depth){
                res.push_back(vector<int>{});
            }
            res[depth-1].push_back(root->val);
        }else {
            return;
        }
        recursionOrder(res, root->left, depth+1);
        recursionOrder(res, root->right, depth+1);

    }


    vector<vector<int> > levelOrder(TreeNode* root) {
        // write code here
        vector<vector<int>> res;
        if(root==NULL){
            return res;
        }
        recursionOrder(res,root,1);
        return res;

    }
};