41.有序数组(二叉搜索树)转平衡二叉树

1.题目描述

2.解题思路

递归，依旧看basecase情况

class Solution {
public:
    
    TreeNode* helper(vector<int>& nums, int l, int r){
        if(l > r){
            return nullptr;
        }
   
    int mid = (l + r)/2;
    TreeNode *root  = new TreeNode(nums[mid]);
    root->left = helper(nums, l , mid - 1);
    root->right = helper(nums, mid + 1, r);
    return root;
}
    
    TreeNode* sortedArrayToBST(vector<int>& nums) {
        return helper(nums, 0, nums.size() - 1);
        
    }
};