题目链接：二叉搜索树的后序遍历序列

import java.util.*;
public class Solution {
    int [] seq;
    public boolean VerifySquenceOfBST(int [] sequence) {
        if(sequence.length <= 0) return false;
        this.seq = sequence;
        return dfs(0, seq.length - 1);
    }

    public boolean dfs(int l, int r){
        if(l >= r) return true;
        int root = seq[r];
        int k = l;
        while(k < r && seq[k] < seq[r]) k ++;
        for(int i = k; i < r; i ++)
            if(seq[i] < root)
                return false;
        return dfs(l, k - 1) && dfs(k, r - 1);
    }
}