1359 · 有序数组转换为二叉搜索树

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题解：

### 解题思路
1.每次随机一个要插入的数字（避免搜索树过度不平衡）
2.插入过的数字，就不在插入了
3.调用Insert1函数进行插入二叉搜索树
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### 题解代码
```
[[cpp]]
/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */

class Solution {
public:
    /**
     * @param nums: the sorted array
     * @return: the root of the tree
     */
    TreeNode* Insert1(TreeNode* root, int node) {
        if (!root) {
            TreeNode* res = new TreeNode(node);
            return res;
        }
        TreeNode* cur = root;
        while (cur) {
            if (node >= cur->val) {
                if (!cur->right) {
                    cur->right = new TreeNode(node);
                    break;
                }
                cur = cur->right;
            } else {
                if (!cur->left) {
                    cur->left = new TreeNode(node);
                    break;
                }
                cur = cur->left;
            }
        }
        return root;
    }
    TreeNode* convertSortedArraytoBinarySearchTree(vector<int> &nums) {
        // Write your code here.
        int len = nums.size();
        if (len <= 0) {
            return nullptr;
        }
        std::unordered_set<int> visited;
        TreeNode* root = nullptr; // 注意，这里必须写初始化！！！！！！！！ 
        while (visited.size() < nums.size()) {
            int index = random() % nums.size();
            if (visited.find(index) != visited.end()) {
                continue;
            }
            visited.insert(index);
            root = Insert1(root, nums[index]); //不断把数组中的节点，插入到树当中
        }
        return root;
    }
};










```