重建二叉树

class Solution 
{
public:
    TreeNode* rebuild(vector<int>& pre, int pre_left, int pre_right, vector<int>& vin, int vin_left, int vin_right) 
    {
        if (pre_left > pre_right || vin_left > vin_right)  return nullptr;
        int root_val = pre[pre_left]; // 记录的是子树根结点上的val值
        TreeNode* root = new TreeNode(root_val);
        for (int i=vin_left; i<=vin_right; ++i) 
        {
            if (vin[i] == root_val) 
            {
                root->left = rebuild(pre, pre_left+1, pre_left+i-vin_left, vin, vin_left, i-1);
                root->right = rebuild(pre, pre_left+i-vin_left+1, pre_right, vin, i+1, vin_right);
                break;
            }
        }
        return root;
    }
    TreeNode* reConstructBinaryTree(vector<int> pre, vector<int>  vin)
    {
        return rebuild(pre, 0, pre.size()-1, vin, 0, vin.size()-1);
    }
};