construct-binary-tree-from-inorder-and-postorder-traversal

Given inorder and postorder traversal of a tree, construct the binary tree.

Note:
You may assume that duplicates do not exist in the tree.

class TreeNode {
     int val;
     TreeNode left;
     TreeNode right;
     TreeNode(int x) { val = x; }
}
public class Solution {
    public TreeNode buildTree(int[] inorder, int[] postorder) {
        if(inorder==null||postorder==null||inorder.length==0||postorder.length!=postorder.length){
            return null;
        }
        return buildTree(inorder,0,inorder.length-1,postorder,0,postorder.length-1);
    }

    private TreeNode buildTree(int[] inorder, int instar, int inend,int[] postorder, int poststar, int postend) {
        if(instar>inend||poststar>postend)return null;
        int value=postorder[postend];
        TreeNode root=new TreeNode(value);
        int index;
        for (index =instar; index < inend&&inorder[index]!=value; index++){
            
        }
        root.left=buildTree(inorder,instar,index-1,postorder,poststar,poststar+index-instar-1);
        root.right=buildTree(inorder,index+1,inend,postorder,poststar+index-instar,postend-1);
        return root;
    }
}