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Update 0106.从中序与后序遍历序列构造二叉树.md

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新增一java寫法 和卡哥的思路一樣的
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Lozakaka
2023-04-23 02:40:34 -04:00
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parent 3466eda7dc
commit b8f6df60c4
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problems/0106.从中序与后序遍历序列构造二叉树.md
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@ -622,7 +622,42 @@ class Solution {
}
}
```
```java
class Solution {
public TreeNode buildTree(int[] inorder, int[] postorder) {
if(postorder.length == 0 || inorder.length == 0)
return null;
return buildHelper(inorder, 0, inorder.length, postorder, 0, postorder.length);
}
private TreeNode buildHelper(int[] inorder, int inorderStart, int inorderEnd, int[] postorder, int postorderStart, int postorderEnd){
if(postorderStart == postorderEnd)
return null;
int rootVal = postorder[postorderEnd - 1];
TreeNode root = new TreeNode(rootVal);
int middleIndex;
for (middleIndex = inorderStart; middleIndex < inorderEnd; middleIndex++){
if(inorder[middleIndex] == rootVal)
break;
}
int leftInorderStart = inorderStart;
int leftInorderEnd = middleIndex;
int rightInorderStart = middleIndex + 1;
int rightInorderEnd = inorderEnd;
int leftPostorderStart = postorderStart;
int leftPostorderEnd = postorderStart + (middleIndex - inorderStart);
int rightPostorderStart = leftPostorderEnd;
int rightPostorderEnd = postorderEnd - 1;
root.left = buildHelper(inorder, leftInorderStart, leftInorderEnd, postorder, leftPostorderStart, leftPostorderEnd);
root.right = buildHelper(inorder, rightInorderStart, rightInorderEnd, postorder, rightPostorderStart, rightPostorderEnd);
return root;
}
}
```
105.从前序与中序遍历序列构造二叉树
```java