Construct Binary Tree from Inorder and Postorder Traversal

public class Solution {
    public TreeNode buildTree(int[] inorder, int[] postorder) {
        // post就是pre的近似倒过来
        if(inorder==null|| postorder==null||inorder.length==0||postorder.length==0) return null;
        return buildTree(postorder, 0, postorder.length-1, inorder, 0, inorder.length-1);
    }
    public TreeNode buildTree(int[] p, int p1, int p2, int[] in, int in1, int in2 ){
        if(p2<p1||in2<in1) return null;
        int len=0;
        while(in[in1+len]!=p[p2]){
            len++;
        }
        TreeNode root = new TreeNode(p[p2]);
        root.left = buildTree(p,p1,p1+len-1,in,in1, in1+len-1);
        root.right = buildTree(p,p1+len,p2-1,in, in1+len+1,in2);
        return root;
    }
}