AC

#include <iostream>
#include <string>

using namespace std;

struct TreeNode {

char val;
TreeNode* left;
TreeNode* right;
TreeNode(char x) : val(x), left(nullptr), right(nullptr) {}

};

TreeNode* buildTree(const string& preorder, int& index) {

if (index >= preorder.size()) {
    return nullptr;
}
char ch = preorder[index++];
if (ch == '.') {
    return nullptr;
}
TreeNode* node = new TreeNode(ch);
node->left = buildTree(preorder, index);
node->right = buildTree(preorder, index);
return node;

}

void inorderTraversal(TreeNode* root, string& res) {

if (root == nullptr) {
    return;
}
inorderTraversal(root->left, res);
res += root->val;
inorderTraversal(root->right, res);

}

void postorderTraversal(TreeNode* root, string& res) {

if (root == nullptr) {
    return;
}
postorderTraversal(root->left, res);
postorderTraversal(root->right, res);
res += root->val;

}

int main() {

string preorder;
cin >> preorder;
int index = 0;
TreeNode* root = buildTree(preorder, index);

string inorder;
inorderTraversal(root, inorder);
cout << inorder << endl;

string postorder;
postorderTraversal(root, postorder);
cout << postorder << endl;

return 0;

}