题目 -> LC102

解题思路

使用一个容器存储节点然后遍历

c++可以使用vector或者deque

python直接使用list也可以deque

代码

Python

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class Solution:
    def levelOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
        if root == None:
            return []
        q = []
        result = []
        q.append(root)
        while q:
            items = []
            res2 = []
            for node in q:
                res2.append(node.val)
                items.append(node.left) if node.left else ...
                items.append(node.right) if node.right else ...
            q = items
            result.append(res2)
        return result

C++

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class Solution {
public:
    vector<vector<int>> levelOrder(TreeNode* root) {
        vector<TreeNode*> q;
        vector<vector<int>> result;
        if (root == NULL) return result;
        q.push_back(root);
        while (!q.empty()) {
            vector<TreeNode*> newq;
            vector<int> res2;
            for (auto node: q) {
                res2.push_back(node->val);
                if (node->left) newq.push_back(node->left);
                if (node->right) newq.push_back(node->right);
            }
            q = newq;
            result.push_back(res2);
        }
        return result;
    }
};