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

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/**
* File: binary_tree_dfs.cpp
* Created Time: 2022-11-25
* Author: krahets (krahets@163.com)
*/
#include "../utils/common.hpp"
// Initialize the list for storing traversal sequences
vector<int> vec;
/* Pre-order traversal */
void preOrder(TreeNode *root) {
if (root == nullptr)
return;
// Visit priority: root node -> left subtree -> right subtree
vec.push_back(root->val);
preOrder(root->left);
preOrder(root->right);
}
/* In-order traversal */
void inOrder(TreeNode *root) {
if (root == nullptr)
return;
// Visit priority: left subtree -> root node -> right subtree
inOrder(root->left);
vec.push_back(root->val);
inOrder(root->right);
}
/* Post-order traversal */
void postOrder(TreeNode *root) {
if (root == nullptr)
return;
// Visit priority: left subtree -> right subtree -> root node
postOrder(root->left);
postOrder(root->right);
vec.push_back(root->val);
}
/* 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);
/* Pre-order traversal */
vec.clear();
preOrder(root);
cout << endl << "Sequence of nodes in pre-order traversal = ";
printVector(vec);
/* In-order traversal */
vec.clear();
inOrder(root);
cout << endl << "Sequence of nodes in in-order traversal = ";
printVector(vec);
/* Post-order traversal */
vec.clear();
postOrder(root);
cout << endl << "Sequence of nodes in post-order traversal = ";
printVector(vec);
return 0;
}