static TreeNode btHelper(int[]A, int s1, int e1, int s2, int e2, Map<Integer, Integer>map) {
		if (s1==e1)
			return null;
		TreeNode node=new TreeNode(A[s1]);
		int mid=map.get(A[s1]);
		node.left=btHelper(A, s1+1,s1+1+mid-s2, s2,mid,map);
		node.right=btHelper(A, s1+1+mid-s2, e1, mid+1, e2, map);
		return node;
	}