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LC107binaryTreeLevelOrderTraversal.cpp
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LC107binaryTreeLevelOrderTraversal.cpp
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/**
* 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) {}
* };
*/
#include <queue>
class Solution {
public:
vector<vector<int>> levelOrderBottom(TreeNode *root) {
vector<vector<int>> res;
if (root == nullptr) return res;
vector<int> init;
TreeNode *preNode = root;
int thisCount = 1;
int nextCount = 0;
int depth = 0;
queue<TreeNode *> Q;
Q.push(root);
while (!Q.empty()) {
preNode = Q.front();
init.emplace(init.begin(), preNode->val);
Q.pop();
thisCount--;
if (preNode->right != nullptr) {
Q.push(preNode->right);
nextCount++;
}
if (preNode->left != nullptr) {
Q.push(preNode->left);
nextCount++;
}
if (!thisCount) {
res.emplace(res.begin(), init);
init.clear();
depth++;
thisCount = nextCount;
nextCount = 0;
}
}
return res;
}
};