【树】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。

public class Solution {
    public boolean VerifySquenceOfBST(int[] sequence) {
        if (null == sequence || 0 == sequence.length) {
            return false;
        }

        return method(sequence, 0, sequence.length - 1);
    }

    public boolean method(int[] nums, int begin, int end) {
        if (begin >= end) {
            return true;
        }

        int root = nums[end];
        int smallCount = 0;
        boolean small = true;
        for (int i = begin; i < end; i++) {
            if(nums[i] < root){
                if(small){
                    smallCount++;
                } else {
                    return false;
                }
            } else {
                small = false;
            }
        }

        return method(nums, begin, begin + smallCount - 1) && method(nums, begin + smallCount, end - 1);
    }
}