[LeetCode]Construct Binary Tree from Inorder and Postorder Traversal

/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
return buildTree(begin(inorder), end(inorder), begin(postorder), end(postorder));
}
private:
TreeNode *buildTree(vector<int>::iterator in_first, vector<int>::iterator in_last,
vector<int>::iterator post_first, vector<int>::iterator post_last) {
if (in_first == in_last) return nullptr;
if (post_first == post_last) return nullptr;

auto val = *prev(post_last);
TreeNode *root = new TreeNode(val);
auto in_root_pos = find(in_first, in_last, val);
auto in_left_size = distance(in_first, in_root_pos);
auto post_left_last = next(post_first, in_left_size);

root->left = buildTree(in_first, in_root_pos, post_first, post_left_last);
root->right = buildTree(next(in_root_pos), in_last, post_left_last, prev(post_last));

}
};