题目描述

blablabla

样例

blablabla

算法1(BFS)

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<vector<int>> printFromTopToBottom(TreeNode* root) {
        queue<TreeNode*> q;
        vector<vector<int>> res;
        if (!root) return res;
        q.push(root);
        while (q.size()) {
            res.push_back({});
            int sz=q.size();
            for (int i=0;i<sz;i++) {
                auto cur=q.front();
                q.pop();
                res.back().push_back(cur->val);
                if (cur->left) q.push(cur->left);
                if (cur->right) q.push(cur->right);
            }
        }
        return res;
    }
};