牛客网--二叉搜索树的后序遍历序列

题目描述

输入一个整数数组，判断该数组是不是某二叉搜索树的后序遍历的结果。如果是则输出Yes,否则输出No。假设输入的数组的任意两个数字都互不相同。

代码

public class Solution {
    public boolean VerifySquenceOfBST(int [] sequence) {
        if(sequence.length == 0)
        {
            return false;
        }
        else if(sequence.length == 1)
        {
            return true;
        }
        return VerifySequenceOfBST(sequence, 0, sequence.length - 1);
    }
    
    private boolean VerifySequenceOfBST(int [] sequence, int start, int end)
    {
        if(start >= end)
        {
            return true;
        }
        int i = start;
        while(i < end && sequence[i] < sequence[end])
        {
            i++;
        }
        for(int j = i; j < end; j++)
        {
            if(sequence[j] < sequence[end])
            {
                return false;
            }
        }
        return VerifySequenceOfBST(sequence, start, i - 1) && VerifySequenceOfBST(sequence, i, end - 1);
    }
}