s0108

include/s0108_convert_sorted_array_to_binary_search_tree.hpp

@@ -0,0 +1,15 @@
+#ifndef S0108_CONVERT_SORTED_ARRAY_TO_BINARY_SEARCH_TREE_HPP
+#define S0108_CONVERT_SORTED_ARRAY_TO_BINARY_SEARCH_TREE_HPP
+
+#include <vector>
+
+#include "structures.hpp"
+
+using namespace std;
+
+class S0108 {
+ public:
+  TreeNode* sortedArrayToBST(vector<int>& nums);
+};
+
+#endif

notes/src/bstree.md

@@ -4,3 +4,4 @@
 - [s0701](https://leetcode.cn/problems/insert-into-a-binary-search-tree/description/): 插入节点。一层一层往下找，直到发现找不到了就在这个地方插入。
 - [s0450](https://leetcode.cn/problems/delete-node-in-a-bst/description/): 删除节点。递归删除。
 - [s0669](https://leetcode.cn/problems/trim-a-binary-search-tree/description/): 修剪 BST 。递归修剪。
+- [s0108](https://leetcode.cn/problems/convert-sorted-array-to-binary-search-tree/): 有序数组转 BST 。数组中点为根节点，中点左侧部分生成左子树，右侧部分生成右子树，递归。

src/s0108_convert_sorted_array_to_binary_search_tree.cpp

@@ -0,0 +1,18 @@
+#include "s0108_convert_sorted_array_to_binary_search_tree.hpp"
+
+TreeNode* sortedArrayToBSTHelper(vector<int>& nums, int begin, int end) {
+  // 找到 nums 的中点
+  int middle = (begin + end) >> 1;
+  // 创建根节点
+  TreeNode *root = new TreeNode(nums[middle]);
+  // 左子树
+  if (middle != begin) root->left = sortedArrayToBSTHelper(nums, begin, middle - 1);
+  // 右子树
+  if (middle != end) root->right = sortedArrayToBSTHelper(nums, middle + 1, end);
+  // 返回根节点
+  return root;
+}
+
+TreeNode* S0108::sortedArrayToBST(vector<int>& nums) {
+  return sortedArrayToBSTHelper(nums, 0, nums.size() - 1);
+}