35 lines
1.3 KiB
Markdown
35 lines
1.3 KiB
Markdown
# 33. 二叉搜索树的后序遍历序列
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[NowCoder](https://www.nowcoder.com/practice/a861533d45854474ac791d90e447bafd?tpId=13&tqId=11176&tPage=1&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking&from=cyc_github)
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## 题目描述
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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。假设输入的数组的任意两个数字都互不相同。
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例如，下图是后序遍历序列 1,3,2 所对应的二叉搜索树。
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<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/13454fa1-23a8-4578-9663-2b13a6af564a.jpg" width="150"/> </div><br>
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## 解题思路
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```java
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public boolean VerifySquenceOfBST(int[] sequence) {
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if (sequence == null || sequence.length == 0)
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return false;
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return verify(sequence, 0, sequence.length - 1);
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}
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private boolean verify(int[] sequence, int first, int last) {
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if (last - first <= 1)
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return true;
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int rootVal = sequence[last];
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int cutIndex = first;
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while (cutIndex < last && sequence[cutIndex] <= rootVal)
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cutIndex++;
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for (int i = cutIndex; i < last; i++)
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if (sequence[i] < rootVal)
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return false;
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return verify(sequence, first, cutIndex - 1) && verify(sequence, cutIndex, last - 1);
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}
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```
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