I have this Accepted solution but I didn't figure out the time complexity of it. Could anyone help?

```
/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public TreeNode buildTree(int[] inorder, int[] postorder) {
return findRoot(inorder, 0, inorder.length-1, postorder, 0, postorder.length-1);
}
private TreeNode findRoot(int[] inorder, int inleft, int inright, int[] postorder, int postleft, int postright){
if(inleft > inright)return null; // base case
int rootVal = postorder[postright]; // the last node in postorder is always the root node
TreeNode root = new TreeNode(rootVal);
// find position of the root node in inorder array
int mid = 0;
for(int i=inleft; i<=inright; ++i){
if(inorder[i] == rootVal){
mid = i;
break;
}
}
int leftNum = mid - inleft; // number of nodes in left part
root.left = findRoot(inorder, inleft, mid-1, postorder, postleft, postleft+leftNum-1); // left subtree is on the left side of the root
root.right = findRoot(inorder, mid+1, inright, postorder, postleft+leftNum, postright-1); // right subtree is on the right side of the root
return root;
}
}
```