/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public TreeNode buildTree(int[] inorder, int[] postorder) {
        return build(0, postorder.length - 1, inorder, postorder);
    }

    public TreeNode build(int start, int end, int[] in, int[] post) {
        if (start > end) return null;
        TreeNode root = new TreeNode(post[post.length - 1]);
        post = Arrays.copyOfRange(post, 0, post.length - 1);
        if (start == end) return root;
        int index = end;
        for (int i = start; i < end; i++) {
            if (in[i] == root.val) {
                index = i;
            }
        }
        root.right = build(index + 1, end, in, post);
        root.left = build(start, index - 1, in, post);
        return root;
    }
}