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Binary Tree Level Order Traversal.cpp
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Binary Tree Level Order Traversal.cpp
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#include <iostream>
#include <queue>
#include <vector>
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:
std::vector<std::vector<int>> levelOrder(TreeNode *root) {
std::vector<std::vector<int>> res;
if (!root) {
return res;
}
std::queue<std::pair<TreeNode *, int>> queue;
queue.push({root, 0});
int current_level = -1;
while (!queue.empty()) {
std::pair<TreeNode *, int> front = queue.front();
queue.pop();
if (front.second == current_level) {
res.back().push_back(front.first->val);
} else {
current_level = front.second;
res.push_back(std::vector<int>{front.first->val});
}
if (front.first->left) {
queue.push({front.first->left, current_level + 1});
}
if (front.first->right) {
queue.push({front.first->right, current_level + 1});
}
}
return res;
}
};