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。如果是则返回true,否则返回false。假设输入的数组的任意两个数字都互不相同。
      示例1
      [4,8,6,12,16,14,10]
      true

*/
public boolean helpVerify(int [] sequence, int start, int root){//递归法
        if(start >= root)return true;
        int key = sequence[root];
        int i;
        //找到左右子数的分界点
        for(i=start; i < root; i++)
            if(sequence[i] > key)
                break;
        //在右子树中判断是否含有小于root的值，如果有返回false
        for(int j = i; j < root; j++)
            if(sequence[j] < key)
                return false;
        return helpVerify(sequence, start, i-1) && helpVerify(sequence, i, root-1);
    }
    public boolean VerifySquenceOfBST(int [] sequence) {
        if(sequence == null || sequence.length == 0)return false;
        return  helpVerify(sequence, 0, sequence.length-1);
 
    }

import java.util.*;
public class Solution {
    //迭代法
    //思路：https://blog.nowcoder.net/n/8fe97e67996249ccbe71328d3a49c4af?f=comment
    public boolean VerifySquenceOfBST(int [] sequence) {
        if(sequence==null||sequence.length==0) return false;
        
        Stack<Integer> stack = new Stack<>();
        stack.push(Integer.MIN_VALUE);
        int max = Integer.MAX_VALUE;
        for(int i = sequence.length-1;i > -1;i--){
            if(sequence[i]>max) return false;
            
            while(sequence[i] < stack.peek()){
                max = stack.peek();
                stack.pop();
            }
            
            stack.push(sequence[i]);
        }
        return true;
    }
}

二叉搜索树的后序遍历序列

原文：https://www.cnblogs.com/chyEric/p/14319442.html