力扣108 將有序數組轉換爲二叉搜索樹 遞歸 左閉右閉

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* sortedArrayToBST(vector<int>& nums) {
        return bst(nums,0,nums.size()-1);
    }
    TreeNode* bst(vector<int>& nums,int l,int r)
    {
        if(r<l) return NULL;
        int mid=l+((r-l)>>1);
        TreeNode* root=new TreeNode(nums[mid]);
        root->left=bst(nums,l,mid-1);
        root->right=bst(nums,mid+1,r);
        return root;
    }
};