【数据结构与算法】根据前序序列重构二叉树

#include <bits/stdc++.h>
using namespace std;
vector<string> a;
int idx = 0;
struct Node {
    string val;
    Node* left;
    Node* right;
    Node(string x):val(x),left(nullptr),right(nullptr){}
};
Node* buildTree() {
    if (idx >= a.size()) return nullptr;
    if (a[idx]=="#") {
        idx++;
        return nullptr;
    }
    Node* node = new Node(a[idx]);
    idx++;
    node->left = buildTree();
    node->right = buildTree();
    return node;
}
void pre(Node* root) {
    if (root == nullptr) {
        return;
    }
    cout<<root->val<<endl;
    pre(root->left);
    pre(root->right);
}
int main() {
    int n;
    string ch;
    cin >> n;
    for (int i = 0;i < n;i++) {
        string b;
        cin>>b;
        a.push_back(b);
    }
    Node* root = buildTree();
    pre(root);
    return 0;
}

       1
     /   \
    2     3
     \   /
      4 5