Construct Binary Tree from Inorder and Postorder Traversal

public class Solution {
    public TreeNode buildTree(int[] inorder, int[] postorder) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        if(inorder == null||postorder == null||inorder.length == 0||postorder.length==0)
            return null;
        return buildTree(inorder, postorder, 0, inorder.length-1, 0 ,inorder.length-1);
    }
    
    private TreeNode buildTree(int[] inorder, int[] postorder, int instart, int inend, int postart, int poend)
    {
        if(instart > inend)
            return null;
        TreeNode node = new TreeNode(postorder[poend]);
        if(instart == inend)
            return node;
        int mid = 0;
        for(int i = instart; i <= inend; i++)
        {
            if(inorder[i] == postorder[poend])
            {
                mid = i;
                break;
            }
        }
        node.left = buildTree(inorder, postorder, instart, mid - 1, postart, postart + (mid - 1 - instart));
        node.right = buildTree(inorder, postorder, mid + 1, inend, poend + mid - inend, poend - 1);
        return node;
    }
}