题目描述
从上到下按层打印二叉树，同一层的节点按从左到右的顺序打印，每一层打印到一行。
https://leetcode.cn/problems/cong-shang-dao-xia-da-yin-er-cha-shu-ii-lcof/
题解
层序遍历
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| class Solution {
public:
vector<vector<int>> levelOrder(TreeNode* root) {
if (!root) return {};
vector<vector<int>> res;
queue<TreeNode*> q;
q.push(root);
while (!q.empty()) {
int curLevelSize = q.size();
res.push_back(vector<int>());
while (curLevelSize--) {
TreeNode* node = q.front(); q.pop();
if (node->left) q.push(node->left);
if (node->right) q.push(node->right);
res.back().push_back(node->val);
}
}
return res;
}
};
|
时间复杂度 O(n)，空间复杂度 O(n)
