还是二叉树的各种基本功

#include <iostream>
#include <vector>
#include <queue>
#include <algorithm>

using namespace std;

struct TreeNode {
  int val;
  TreeNode* left;
  TreeNode* right;
  TreeNode() : val(0), left(nullptr), right(nullptr) {};
  TreeNode(int _val) : val(_val), left(nullptr), right(nullptr) {};
  TreeNode(int _val, TreeNode* _left, TreeNode* _right) : val(_val), left(_left), right(_right) {};
  ~TreeNode() {};
};

int n, l, r;

TreeNode* buildTree(vector<pair<int, int>>& node_infos, int index) {
  // recursion exit condition
  if (index == -1) return nullptr;

  auto root = new TreeNode(index);
  root->left  = buildTree(node_infos, node_infos[index].first);
  root->right = buildTree(node_infos, node_infos[index].second);
  return root;
}

void fill(TreeNode* root, vector<int>& vals, int& idx) {
  if (!root) return;
  fill(root->left, vals, idx);
  root->val = vals[idx++];
  fill(root->right, vals, idx);
}

void levelOrder(TreeNode* root) {
  queue<TreeNode*> q{{root}};
  while (not q.empty()) {
    auto cur = q.front(); q.pop();
    printf("%d ", cur->val);
    if (cur->left)  q.emplace(cur->left);
    if (cur->right) q.emplace(cur->right);
  }
}

int main(void) {
  scanf("%d", &n);
  vector<pair<int, int>> node_infos(n);
  for (int i = 0; i < n; ++i) {
    scanf("%d %d", &l, &r);
    node_infos[i] = {l, r};
  }

  vector<int> vals(n);
  for (int i = 0; i < n; ++i) cin >> vals[i];
  sort(begin(vals), end(vals));

  auto root = buildTree(node_infos, 0);

  int idx = 0;
  fill(root, vals, idx);

  levelOrder(root);
}