[剑指offer] 4. 重建二叉树

class Solution
{
public:
  TreeNode *reConstructBinaryTree(vector<int> pre, vector<int> vin)
  {
    return helper(pre, 0, pre.size() - 1, vin, 0, vin.size() - 1);
  }

  TreeNode *helper(vector<int> pre, int pbeg, int pend, vector<int> vin, int vbeg, int vend)
  {
    if (pbeg > pend || vbeg > vend)
      return NULL;
    TreeNode *res = new TreeNode(pre[pbeg]);
    int index = 0;
    while (index < vend)
    {
      if (vin[index] == pre[pbeg])
        break;
      index++;
    }
    cout << res->val << endl;
    res->left = helper(pre, pbeg + 1, pend + index - vbeg, vin, vbeg, index - 1);
    res->right = helper(pre, pbeg + 1 + index - vbeg, pend, vin, index + 1, vend);
    return res;
  }
};