题解 | #把二叉树打印成多行#

层次遍历二叉树，按层push就解决了，关键是树的level变量！！！

/*
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> > res;
	    void PrintLevel(TreeNode* pRoot,int level){
        	if(pRoot == NULL){
            return;
        }
        if(res.size() < level + 1){
            res.push_back({});
        }
        res[level].push_back(pRoot->val);
        PrintLevel(pRoot->left,level+1);
        PrintLevel(pRoot->right,level+1);
    }
    vector<vector<int> > Print(TreeNode* pRoot) {
        PrintLevel(pRoot, 0);
        return res;
    }
};