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hello-algo/en/codes/cpp/chapter_tree/binary_tree_bfs.cpp

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/**
* File: binary_tree_bfs.cpp
* Created Time: 2022-11-25
* Author: krahets (krahets@163.com)
*/
#include "../utils/common.hpp"
/* Level-order traversal */
vector<int> levelOrder(TreeNode *root) {
// Initialize queue, add root node
queue<TreeNode *> queue;
queue.push(root);
// Initialize a list to store the traversal sequence
vector<int> vec;
while (!queue.empty()) {
TreeNode *node = queue.front();
queue.pop(); // Queue dequeues
vec.push_back(node->val); // Save node value
if (node->left != nullptr)
queue.push(node->left); // Left child node enqueues
if (node->right != nullptr)
queue.push(node->right); // Right child node enqueues
}
return vec;
}
/* Driver Code */
int main() {
/* Initialize binary tree */
// Use a specific function to convert an array into a binary tree
TreeNode *root = vectorToTree(vector<int>{1, 2, 3, 4, 5, 6, 7});
cout << endl << "Initialize binary tree\n" << endl;
printTree(root);
/* Level-order traversal */
vector<int> vec = levelOrder(root);
cout << endl << "Sequence of nodes in level-order traversal = ";
printVector(vec);
return 0;
}