力扣 102. 二叉树的层序遍历🔗 https://leetcode.cn/problems/binary-tree-

题目

按照层输出

思路

队列

代码

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    vector<vector<int>> levelOrder(TreeNode* root) {
        vector<vector<int>> vec;
        if (root == nullptr) return vec;
        queue<TreeNode*> que;
        que.push(root);
        while (!que.empty()) {
            int size = que.size();
            vector<int> tmp;
            while (size--) {
                TreeNode* node = que.front();
                tmp.push_back(node->val); que.pop();
                if (node->left) que.push(node->left);
                if (node->right) que.push(node->right);
            }
            vec.push_back(tmp);
        }
        return vec;
    }
};