106.construct binary tree from post order and inorder

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public TreeNode buildTree(int[] ino, int[] post) {
        Map<Integer,Integer> mp=new HashMap<>();
        for(int i=0;i<ino.length;i++){
            mp.put(ino[i],i);
        }
       return rec(ino,post,0,ino.length-1,0,post.length-1,mp);        
    }
    static TreeNode rec(int[] ino,int[] post,int ins,int ine,int posts,int poste,Map<Integer,Integer>mp){
        if(ins>ine||posts>poste){
            return null;
        }
        TreeNode root=new TreeNode(post[poste]);
        int l=mp.get(root.val);
        int length=l-ins;
        root.left=rec(ino,post,ins,l-1,posts,posts+length-1,mp);
        root.right=rec(ino,post,l+1,ine,posts+length,poste-1,mp);

        return root;

    }
}