题解 | #JZ78 把二叉树打印成多行#

//使用两层队列按左右子节点数据遍历
/*
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>> retvec;
            queue<TreeNode*> cur, next;
            
            if (pRoot) cur.push(pRoot);    //当前层压入根节点
            
            while (cur.size()) {
                vector<int> vec;
                
                while (cur.size()) {    //遍历当前层节点，存储值，左右节点存入下一层
                    TreeNode *node = cur.front();
                    cur.pop();
                    
                    vec.push_back(node->val);
                    
                    if (node->left) next.push(node->left);
                    if (node->right) next.push(node->right);
                }
                
                if (vec.size()) retvec.push_back(vec);
                
                cur.swap(next);    //当前层为空，与下一层交换
            }
            
            return retvec;
        }
    
};