二叉树搜索树的后序遍历序列

Posted 2021-02-11 wylwyl

题目：

输入一个整型数组，判断该数组是不是二叉搜索树的后序遍历结果。

如果是，返回true。否则返回false

 

解答：

 1 public class Solution {
 2 
 3     public static boolean VerifySquenceOfBST(int[] squence) {
 4         return VerifySquenceOfBST(squence, squence.length);
 5     }
 6 
 7     private static boolean VerifySquenceOfBST(int[] squence, int length) {
 8         if(squence == null || length == 0) {
 9             return false;
10         }
11 
12         int root = squence[length-1];
13 
14         int i = 0;
15         for(; i < length-1; i++) {
16             if(squence[i] > root) {
17                 break;
18             }
19         }
20 
21         int j = i;
22         for(; j < length-1; j++) {
23             if(squence[j] < root) {
24                 return false;
25             }
26         }
27 
28         boolean left = true;
29         if(i > 0) {
30             left = VerifySquenceOfBST(squence, i);
31         }
32 
33         boolean right = true;
34         if(i < length-1) {
35             right = VerifySquenceOfBST(squence, length-i-1);
36         }
37 
38         return left&&right;
39     }
40 }