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102.二叉树的层序遍历.cpp
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102.二叉树的层序遍历.cpp
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/*
* @lc app=leetcode.cn id=102 lang=cpp
*
* [102] 二叉树的层序遍历
*/
// @lc code=start
/**
* 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>> levelOrder(TreeNode* root) {
if (!root) return {};
vector<vector<int>> ans;
int now = 1, next = 0;
queue<TreeNode * > q;
q.push(root);
vector<int> tmp;
while (q.size()) {
TreeNode * t = q.front();
q.pop();
now -- ;
tmp.push_back(t->val);
if (t->left) {
q.push(t->left);
next ++ ;
}
if (t->right) {
q.push(t->right);
next ++ ;
}
if (now == 0) {
now = next;
next = 0;
ans.push_back(tmp);
tmp.clear();
}
}
return ans;
}
};
// @lc code=end