剑指offer 二叉搜索树的后序遍历序列

import java.util.Arrays;
public class Solution {
    public boolean VerifySquenceOfBST(int [] sequence) {
        int len = sequence.length;
        if (sequence == null || len == 0)
            return false;
        return isBST(sequence);
    }
    public boolean isBST(int [] sequence) {
        int mid = 0, len = sequence.length;
        if (len <= 1) {
            return true;
        }
        for (; sequence[mid] < sequence[len - 1]; mid++);
        for (int i = mid; i < len - 1; i++)
            if (sequence[i] < sequence[len - 1])
                return false;
        return isBST(Arrays.copyOfRange(sequence, 0, mid)) &&
                isBST(Arrays.copyOfRange(sequence, mid, len - 1));
    }
}